CONCHOLOGY. 



Animal longer than its shell, furnished 

 with four tentacula, the two superior ones 

 longer, cylindrical, supporting the eyes ; 

 inferior ones, short, conic. Colour pale 

 with minute black points, which are as- 

 sembled into fascia on the sides and fil- 

 lets on the neck above ; neck granulate 

 above, a black line passes each side on the 

 neck, from the tip of the oculiferous ten- 

 tacula, gradually disappearing under the 

 shell. Front truncate, quadrate. 



When the animal 5s living, so vitreous 

 is the shell, that all the markings of its 

 body are plainly discernible. So that al- 

 though the shell is of a straw-colour, im- 

 maculate, it appears of a dusky hue, with 

 a remarkable white, flexuous, longitudi- 

 nal vitta on the back, arising from the su- 

 ture, and terminated about mid way to the 

 base, often with two or three obsolete 

 white spots near its tip. 



The characters of the inhabitants are 

 widely distinct from the animal of the 

 Lymnxa, and are somewhat allied to those 

 of the inhabitants of the Helices. 



GENT7S CTCLOSTOMA. 



A subdiscoidal or conic univalve. The 

 aperture orbicular, with a circularly con- 

 tinued margin, often, suddenly and wide- 

 ly reflected. 



SPECIES. 



C. Tricarinata. Shell with three volu- 

 tions ; three revolving, carinate, promi- 

 nent lines, giving to the whorls a quad- 

 rate, instead of a cylindric appearance. 

 Suture canaliculate, in consequence of 

 the whorls revolving below the second 

 carina and leaving an interval. Spire 

 convex, apex obtuse. Umbilicus large. 

 Carina placed, one on the upper edge of 

 the wherl, one on the lower edge, and the 

 third on the base beneath. Breadth one- 

 fifth of an inch. 



Inhabits the river Delaware. Rare. 



Found by Mr. Le Sueur, whose pro- 

 posed name is here adopted. 



GEJTUS ANCYCLUS. GEOFF. LATH. 



Shell conic, not spiral, concave be- 

 neath, above with a simple apex. 



Animal with the eyes placed at the in- 

 ner base of the tentacula. 



Observation. This genus has been con- 

 founded with the Patellae. The European 

 speeies are Patella Laciistris, and Fhmia* 

 tilis, of Linne. 



SPECIES. 



Jl. rivularis. Shell corneous, opake, 

 conic-depressed ; apex obtuse, nearer to, 

 and leaning towards one side and one 

 end ; aperture oval, rather narrower at 

 one end, entire ; within milk white. 



Length one-fourth of an inch. 



Journ. Acad. Nat. Sciences, vol. i. p. 124. 



Common in rivulets, adhering to stones. 

 The animal resembles the inhabitant of 

 shells of the genus Lymnsea, the tail is 

 very obtuse, rounded. 



GENUS PALUWDINA. LAM. LATH. 



Shell subovate, operculated; aperture 

 entire, longitudinally ovate, narrowed 

 above ; lip simple, not dilated or re- 

 flected. 



Observation. This genus has been very 

 lately separated by Mr. Lamarck from the 

 Cyclostonue, with which it corresponds, 

 except in having no dilated lip, and the 

 aperture is angulated above. The animal 

 has a short rostrum, two acute tentacula 

 with eyes at their external base, a small 

 membranaceous wing each side of the 

 body before, foot double before, the wing 

 of the right side is folded into a small ca- 

 nal, by which the water is introduced into 

 the respiratory canal. Latr. 



\. P. Limosa. Shell conic, subumbili- 

 cate, dark horn coloured, generally in- 

 crusted with a blackish irregular covering 

 on the spire, and sometimes on the body, 

 which completely obscures the obsolete- 

 ly wrinkled epidermis ; aperture ovate- 

 orbicular ; suture impressed. 



Length three-twentieths, breadth one- 

 tenth, of an inch. 



Journ. JLcad. Nat. Sciences, vol. i. p. 125. 



Animal whitish ; head brown ; mouth, 

 tentacula, orbits, and vita on each side of 

 the neck, white ; tentacula filiform, more 

 than half as long as the base of the ani- 

 mal ; rostrum about half as long as the 

 tentacula, annulate, with darker lines 

 above ; foot white, brownish above, short, 

 suboval, truncated before, and rounded 

 behind. 



Extremely numerous on the muddy 

 shores of the rivers Delaware and Schuyl- 

 kill, between high and low water marks. 



2. P. lapidana. Shell turreted, subum- 

 bilicate, with six volutions, which areob- 

 soletely wrinkled across. Suture im- 

 pressed. Aperture longitudinally ovate- 



