214 PROCEEDINGS OF THE ACADEMY OF [1883. 



ON THE ANATOMY OF ANCYLUS FLUVIATILIS 0. F. Muller AND 

 ANCYLUS LACUSTRIS Geoffrey. 



BY BENJAMIN SHARP, M. D., PH. D. 



This paper first was written in German, and served as an 

 inaugural dissertation for the Philosophical faculty at the Uni- 

 versity of Wiirzburg, in Bavaria. In rewriting it I have merely 

 omitted a few unimportant details, and made one or two slight 



changes. 



Introduction. 



The position of these little animals in the system of classifica- 

 tion was long a subject of dispute. At first they were placed by 

 Linnaeus ^ in the genus Patella, but in the same year (1767) 

 Geoff"roy^ formed an especial genus for them, which he called 

 Ancylus, on account of the resemblance of the shell to a Pliygean 



cap (A'yX'"5oO. 



The specimens of Jiuvialilis, which I had for examination, were 

 obtained in the Main near Wiirzburg, and in a branch of the same 

 near Gemiinden — the only place in which the other species could 

 be had was in a small pond near Aschaffenburg. 



The work was carried on in the laboratory of Prof C. Semper, 

 at Wiirzburg, and I here take the opportunit}^ of expressing my 

 sincere thanks to him for his kindly advice and assistance. 



Ferussac placed this genus, in 1837, among the Pulmonata, to 

 which order it undoubtedly belongs. 



Moquin-Tandon ^ believed that Ancylus was amphibian in its 

 habits. I do not believe that the animal under natural and healthy 

 conditions ever approaches the surface of the water. He says : 

 " Does the animal breathe free air or that air dissolved in water?" 

 Ferussac * said positively that the animal was compelled to come 

 to the surface to breathe. L. Agassiz,^ Depuy, and others, were 

 of the same opinion. To prove this, Moquin-Tandon ^ made the 

 following experiments : — 



1 Linnseus, Syst. Nat., 1767. 



2 Geoffroy, Trait, somm. d. Coquil fluv. et terres., etc., Paris, 1767. 



^ Moquin-Tandon, Recher. anatomico-physiol. sur I'Ancyle fluviatile 

 {Ancylus fluviatilis), Journal de Concbyliologie, Tome ill, 1852, p. 12-1. 

 * Ferussac, Diet, class, d. Hist. Nat., Tome i, 1822. 

 ^ L. Agassiz, Act. Helvit., 1841. 

 ^ Eeclier. anat. i^hysiol. s. I'Ancyle, etc., pp. 124-126. 



