Dr. Rob Dillon, Coordinator

Wednesday, February 6, 2019

Ferrissia fragilis (Tryon, 1863)

Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c)  Ferrissia fragilis (Tryon, 1863).  Pp 207 – 214 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other EssaysFWGNA Project, Charleston, SC.

At 9:30 on the starry but moonless night of April 16, 1863, seven armored gunboats under the command of Admiral David Porter, accompanied by three army transports and a steam ram, began a stealthy voyage down the Mississippi under the guns of Vicksburg.  Water-soaked bales of hay were stacked around their boilers and pilot houses, and coal barges lashed to their starboard flanks.  At 11:10 PM, all hell broke loose [1].

Wikimedia Commons
On the evening of April 20, four days later, the regular biweekly meeting of the California Academy of Natural Sciences convened at 622 Clay Street, San Francisco, seven members present, Dr. Trask in the chair.  Dr. Cooper communicated the description of a new mollusk, recently discovered by Rev. Joseph Rowell in the waters of the Feather River, Gundlachia californica [2].  Images of the little limpet, “length about sixteen one-hundredths of an English inch,” showed a shell apex distinctly different from the embryonic shell origin.  Philip Lutley Sclater, Esq., of London was elected a corresponding member, three species of reptiles from San Mateo added to the cabinet, and the Academy adjourned.

Shortly after 5:00 on the evening of May 2, 1863, the troops on the right flank of General Joseph Hooker’s army at Chancellorsville, VA, stacked their rifles and began to prepare their suppers.  They were amused to see large numbers of deer and rabbits break out of thickets to the west and come bounding toward them.  The men cheered and waved their caps at the startled forest creatures, until the next thing they saw froze the laughter in their throats.  Total casualties at the end of the battle were 3,500 killed and 19,000 wounded.

May 2, Just before dawn.  Wikimedia commons
A bit more than two weeks later, on the afternoon of May 26, 1863, The Academy of Natural Sciences of Philadelphia convened for its regular weekly meeting, 19 members present, Mr. Lea in the chair.  The agenda was lengthy: 9 papers presented and ordered to be published, including an ambitious contribution by T. B. Wilson & J. Cassin proposing a third kingdom of life, the Primalia.  Mr. George W. Tryon read a paper describing seven new species of freshwater gastropods, finishing with Ancylus fragilis [3].  The 4 millimeter limpet, apex elevated, acute and “curved backwards,” had been sent to him from California by Rev. J. Rowell.

On June 3, 1863, General Robert E. Lee began to concentrate his army of 75,000 at Culpeper, in preparation for an invasion northward.  And on the morning of June 8, Union General Alfred Pleasonton probed south across the Rappahannock with six brigades of cavalry, approximately 10,000 horsemen, to gauge Lee’s disposition.  Around noon Pleasonton encountered a roughly equal force of confederate cavalry under Gen. Jeb Stuart at Brandy Station.  Sabers, pistols, and carbines flashing in the sun, the largest cavalry engagement ever fought on American soil was underway.

Cavalry Charge Near Brandy Station, by Edwin Forbes.
Two weeks later, on the afternoon of June 17, the Boston Society of Natural History convened at Tremont Street, Prof. Wyman in the chair.  Mr. Stimpson read a paper on the genus Gundlachia, in which he counted five species, including G. californica, described just two months prior [4].  He went on to describe a sixth species, G. meekiana, collected from the vicinity of Washington DC, similar in all respects to G. californica, but with a less ovate aperture.  One additional paper was read, two communications received, six donations to the museum logged, and the Society adjourned.

Admittedly, the little brown pulmonate limpet that we today call Ferrissia fragilis is not the most striking element of the North American malacofauna.  It is, however, the fourth most common freshwater gastropod in the Eastern United States, behind Physa acuta, Campeloma decisum, and Menetus dilatatus [5].  Populations of Ferrissia fragilis are ubiquitous on aquatic vegetation and organic debris in every lake, pond, and riverine backwater nationwide, Canada to Mexico, sea to shining sea.  Including at the mouth of Pennypack Creek, in north Philadelphia.

Why do you suppose that these exceptionally abundant and wide-ranging little gastropods were completely overlooked by every American biologist working in every puddle of fresh water for half a century, and then simultaneously discovered by three completely separate societies of learned men, meeting in San Francisco, Philadelphia, and Boston, during a single eight-week period of 1863?  What might account for the sudden, passionate interest among young well-born gentlemen of the urban North in freshwater limpets?  I will leave that question to the speculation of my readership.

The Bartow County Yankee Killers [6]
I will, however, take a paragraph to remind you all of several previous essays touching upon Ferrissia fragilis [7].  You may recall, from my essays of 10June09 and 9Nov12, that the freshwater limpets were a particular research interest of Bryant Walker’s (1856 – 1936), and that the definitive monograph was contributed by Paul Basch in 1963 [8].  Both Walker and Basch recognized Ferrissia fragilis as a widespread and important element of the North American malacofauna, and listed californica (Rowell 1863) and meekiana (Stimpson 1863) as junior synonyms of fragilis (Tryon 1863).  And you may also remember my essay of 8Dec10 reviewing the excellent work of Andrea Walther and colleagues [9] synonymizing several additional well-known names under fragilis, including walkeri (Pilsbry & Ferris 1906) and mcneilli (Walker 1925).  So that today, the FWGNA Project recognizes just two species of Ferrissia: rivularis and fragilis.

Up until recently it has been quite easy to ignore the extraordinarily trivial and obscure detail that the meeting of the California Academy which heard the description of G. californica preceded the meeting of the ANSP which heard the description of A. fragilis by five weeks.  And that Rowell's publication preceeded Tryon's by six.  For some reason that I cannot fathom, however, here in 2019 it has become less easy.

The issue of the American Malacological Bulletin freshly arrived on my desk last month included a research note announcing the “discovery of the freshwater limpet, Ferrissia californica (Rowell, 1863)” on the Island of Montserrat [10].  Tryon’s nomen “fragilis” does not appear in title, abstract, key words, or the first five paragraphs of its introduction.

Do systematic biologists of the 21st century feel some heightened sense of obligation to the Rev. Rowell, now asleep in Christ for 100 years?  Have our oaths to uphold the International Code of Zoological Nomenclature suddenly become more solemn?  Is the iron fist of the ICZN Commission grown more fearsome?

I do not know.  I am neither priest nor scribe nor Pharisee, I am a scientist.  The names I assign to populations of freshwater gastropods are hypotheses of evolutionary relationship – my best hypothesis, without compromise.  If I find that more than one name has been assigned to a population or group of populations, each of which conveys the same evolutionary hypothesis, I will select the name that, in my judgement, conveys my hypothesis to the broadest audience. 

The best name for North American freshwater limpets with an eccentric shell apex is Ferrissia fragilis (Tryon, 1863).  The letter of some legalistic code about which I was not consulted, administered by some commission I do not recall electing, does not enter into the calculation.

But let me hasten to make another point, and to make it as forcefully as I have made the previous one.  I would not presume to impose my selection of any scientific name on anyone else.  In fact, I earnestly hope that other scientists will develop other hypotheses about the evolutionary relationships of the populations I refer to Ferrissia fragilis.  Such a situation would be the mark of an active science.  And if it is the judgement of some other worker that Rowell’s nomen californica transmits information more effectively than Tryon’s fragilis, far be it from me to second-guess.

I have no problem with synonyms.  I do not think that taxonomic synonyms necessarily lead to scientific confusion, any more than I expect the college dean to become confused if I tell him to kiss my peachy-pink posterior or my rosy-red ass, on the way out the door.  Synonyms are pervasive in the English language, and we are richer for it.

Indeed, I think it will be a service to preserve both names.  So just this morning I have added Rowell’s “Ferrissia californica” directly under the header “Ferrissia fragilis” at the top of my FWGNA page.  And entered the nomen into the list of synonyms available from the website pull-down.  And written the present essay, wherein both names are connected.  In this fashion, the future generation of graduate students, perhaps naïve about the fragilis/californica situation, will be able to google-up and connect their disparate literatures.

And finally.  Difficult though it may be to understand [11], some non-negligible fraction of my colleagues have, from time to time, associated into committees to develop formal lists of accepted or approved names that we, “the community,” will be sanctioned to apply to the diverse biota of this, our great country.  I would suggest that all members of such committees re-read the first six paragraphs of the present essay.  And get a life, every one of you.


[1] This account of the action at Vicksburg, together with those of Chancellorsville and Brandy Station following, are extracted from Shelby Foote’s (1963) classic The Civil War, A Narrative.  Volume II, Fredricksburg to Meridian. Vintage Books, 988 pp.

[2] Rowell, J (1863) Description of a new Californian Mollusc.  Proceedings of the California Academy of Sciences Series 1, 3: 21 – 22.

[3] Tryon, G. W. (1863) Descriptions of new species of fresh water Mollusca, belonging to the families Amnicolidae, Valvatidea, and Limnaeidae; inhabiting California.  Proc. Acad. Natl. Sci. Phila. 15: 147 – 150.

[4] Stimpson, W. (1863) Malacozoological Notices No. 1, On the genus Gundlachia.  Proc. Boston Nat. Hist. Soc. 9: 249 -252.

[5] This result is from 18,974 records of 99 species in four regions: the Atlantic, the Ohio, East Tennessee, and (very preliminarily) The Cumberland.  Download the presentation here:
  • The freshwater gastropods of The Ohio: An interim report [27June17]
[6] From left, Daniel, John, and Pleasant Chitwood of Company A, 23rd Georgia Infantry.  Daniel and John were captured at Chancellorsville on May 2, 1863.  This image scanned from Miller, W J. & B. C. Pohanka (2006).   An Illustrated History of the Civil War.  Barnes & Noble.

[7] My previous essays on Ferrissia:
  • Just One Species of Ferrissia [10June09]
  • Two Species of Ferrissia [8Dec10]
  • Bryant Walker’s Sense of Fairness [9Nov12]
[8] Basch, P.F. (1963) A review of the recent freshwater limpet snails of North America (Mollusca: Pulmonata). Bull. Mus. Comp. Zool. Harvard Univ. 129: 399–461.

[9] Walther, A. C., J. B. Burch and D. O’Foighil (2010) Molecular phylogenetic revision of the freshwater limpet genus Ferrissia (Planorbidae:Ancylinae) in North America yields two species: Ferrissia (Ferrissia) rivularis and Ferrissia (Kincaidilla) fragilis. Malacologia 53: 25-45.

[10] Coote, T, K. A. Schmidt, R. E. Schmidt, & E. R. McMullin (2018) Discovery of the freshwater limpet, Ferrissia californica (Rowell, 1863) (Gastropoda: Planorbidae), from streams of Montserrat, West Indies, a new addition to the Caribbean fauna.  American Malacological Bulletin 36: 291 – 295.

[11] I myself probably do understand it, however.  I think committees form to standardize the names of the diverse elements of the American biota to facilitate governmental regulation.  And with governmental regulation comes governmental funding.  I don’t want to be cynical – I’m pretty sure my colleagues on such committees think that they are furthering the cause of conservation, and that whatever taxpayer’s dollars might be expended on their salaries are well-justified.  I used to think that, too.


  1. I'm calling you out in regards to you claim that you would not "I would not presume to impose my selection of any scientific name on anyone else."

    You've forcefully defended and argued for GenBank imposing your ridiculous concept of pleurocerid taxonomy on others (notably that all Elimia should be considered Pleurocera).

    You really should stop taking a holier than thou approach to your blogging. And hopefully the people who read your blog don't take any of it seriously.

    Your condescending tone towards other people is really something else.

    You should take your own advice, and get a life

  2. You really need to be called out for the complete mischaracterization you made of yourself. You've strongly advocated for NCBI/GenBank forcing your perspectives of pleurocerid taxonomy onto others. To say you would never impose your selection of scientific names on others is nonsense.

    And the negative ways you talk about others on this blog is really something else. You really should take your own advice and get a life.