502 LIMNiEID^. 



A. tardus^ Say, which has been found by Professor Adams in Ver- 

 mont, but which 1 have not yet found in this State. It is nuich 

 more rounded and conical than this, and the apex is not lateral. 



Ancylus fuscus. 



Fig. 152. 



Shell oval, depressed, convexity regular, not compressed laterally, curvilinear 

 at the sides; apex obtuse, a little to the right and rear of the centre; epidermis 

 coai'se, brown, surpassing the margin. 



Ahci/Ius fuscus, Adams, Best. Joiirn Nat. Hist. iii. 329, pi. 3, fig. 17 (1840) ; Am. Journ. 

 Sc. [i], xxxviii. 396 (1840). — Haldeman, Mon. 12, pi. 1, fig. 7 ( 1844). — Gould, 

 Inv. 224., fig. 152 (1841). — De Kay, N. Y. Moll. 13 (1843). — Anon. Can. Nat. ii. 

 212, fig. (1857). — W. G. BiNNEY, Smith. Inst. L. and Fr. W. Shells, ii. 140, fig. 

 233 (1865). 



Shell small, very thin and pellucid, of a rounded oval form, the 



entire outline regularly curved ; depressed and regularly convex, 



not compressed at the sides ; apex slightly elevated, bluntly 



Fig. 753. j,Q^^j^(j^3j ^ ii^-^iQ behind, and to the right of the centre ; stages 



, 7 of arowth visible ; eiiidermis coarse and strong, rough, dusky 



A' fits- o ^ ^ 



'"'■ yellowish-ljrown, extending beyond the margin of the testa- 



Enlarged. -^ *" , . •/! -i 11 'J 



ceous matter, and insensibly coalescing witli it on ail sides, 

 Avhich are inclined to turn upwards; within glistening, polished. 

 Length, three tenths of an inch ; height, one tw-entieth of an inch ; 

 breadth, twenty-two one hundred and sixtieths of an inch. 



Found in a rivulet in Andover by Mr. K. Prescott, of the Theo- 

 logical Seminary; and also ibund liy Professor Adams in Mans- 

 field ; and by myself in Fresh Pond. 



It differs from all other described species in its depressed form, 

 its obtuse apex, and its coarse epidermis projecting beyond the mar- 

 gin ; and, as this extends in the direction of the plane of the object 

 to which it is found attached, and not in continuation of the convex 

 form of the shell, the edges seem to be turned upwards. A. paral- 

 lelus is narrow^er, and has the sides nearly parallel. A. tardus, Say, 

 has its apex prominent, acute, and farther behind the middle. 

 [It has also been found in Ohio and the District of Columbia. 



