FAMILY HEMIPHYLLIDIA ANCYLUS. 13 



Ancylus CALCARIUS. 



PLATE V. FIG. 99. a. b. — (STATE COLLECTION.) 



Description. Shell conic, calcareous, opake. Apex not central, moderately prominent. 

 Aperture oval, entire ; the curves on the longest sides dissimilar. In very minute specimens, 

 the edges somewhat everted. 



Color. Epidermis rufous, extending beyond the edges of the aperture ; within, bluish 

 white, darker towards the apex. 



Length, 0-3. Height, 0-12. 



The specimen which furnished the above description was one of the largest which I have 

 seen. They are more commonly of the dimensions of A. rivularis. I separate it from this 

 latter, chiefly on account of its solid calcareous structure. I am indebted to Mr. I. Cozzens 

 for the specimens from the Passaic river, near Patterson ; but it will doubtless be found in 

 this State. 



Ancylus fuscus. 



A. fuscus. Adams, Bost. Jour. Nat. Hist. Vol. 3, p. 329, pi. 3, fig. 17. 

 A. id. Gould, Invertebrata Mass. p. 224, fig. 152. 



Description. Shell rounded oval, the entire outline regularly curved, thin and pellucid, 

 depressed ; convexity regular, not compressed at the sides. Apex obtuse, a little to the 

 right of the centre. Epidermis coarse, strong and rough, extending beyond the margin of the 

 shell. 



Color. Epidermis dusky yellowish brown ; within, glistening, polished. 



Length, 0-3. Height, 0-01. 



This species has been observed in Massachusetts, and will probably be found in this State. 

 It appears to be a very distinctly marked species. 



(EXTRA-LIMITAL.) 



A. tardus. (Say, Des. terr. et fluv.) Shell conic, depressed. Apex behind the middle, obtuse, rounded, 

 inclining backwards, but not laterally. Line from the apex to the posterior tip rectilinear ; line 

 from the apex to the anterior tip arcuated. Aperture oval, not distinctly narrowed at one end. 

 Length, 0*15; breadth, • 1. Wabash River. 



A. filosus. (Conrad, Fresh Water Shells, p. 57.) Shell regularly oval, rather elevated, with nu- 

 merous radiating prominent lines. Apex very prominent, inclined, eroded, not nearly central. 

 Abundant on Melania. Alabama. 



A. nuttallii. (Hald. Monog. Lymn. No. 3.) Shell oval, elevated. Apex one-fourth of the entire 

 length from one end. Color fuscous. Length, 0-3; breadth, 0-25; height, 0*09. Oregon. 



A. diaphanus. (Hald. lb.) Shell regularly oval, very wide, depressed. Apex sub-central. Color, 

 very pale, translucent. Length, 0*25. Ohio. 



A parallelus. (Hald. Adams, Am. Jour. Vol. 40, p. 275.) 



