THE NAUTILUS. 



The reference of the specimens from Rock Run, Joliet, Ills., to this 

 species by Baker (Moll. Chic. Area, p. 306), is erroneous fof the 

 same reason. 



The A. sltimekii is a very distinct, little species, and, when once 

 seen, is not likely to be mistake-n for any other. The high, narrow 

 shell with the rapid expansion towards the base ; the prominent, 

 excentric, deflected apex, almost reaching the posterior margin, the 

 long convex anterior slope, -and the peculiar posterior slope are very 

 characteristic and separate it from all the described .species. It is 

 more nearly related to the small Ohio species, called pumilus by 

 Sterki, than to any other, but is clearly distinct as pointed out under 

 that species. 



The specimen figured, the largest received from Shimek, is 

 slightly smaller than 1 the average size as stated in the original de- 

 scription, being : 

 1 Length 2.66, breadth 1.66, alt. 1.0 mm. 



X. Ancylus pumilus Sterki (1900). PI. 6, figs. 20-22. 

 ' 1894. Ancylus -? Sterki. The L. & F. W. Moll, of New 

 Pliila.,O., sp. 83, p. 8. 



1900. Ancylus pumilus Sterki. List of L. & F. W. Moll, of 

 Tuscawaras- Co., O., 8th, An. Rep. 0. St. Acad. Sci., p. 36, 

 Separate p. 7. 



Shell small, thin, translucent, shining, horn-colored; oval or 

 slightly obovate ; ends regularly rounded ; sides nearly equally 

 curved ; apex radially striate, prominent, rather obtuse, not depressed 

 at the tip, about half way between the central and posterior margin 

 and decidedly turned to the right ; anterior and left slopes very con- 

 vex ; left slope nearly straight ; posterior slope straight below the 

 projecting apex ; surface with the lines of growth fine and incon- 

 spicuous, more or less irregularly rippled with transverse wrinkles 

 on the anterior slope. 



Fig. 20. Length 2.75, breadth 1.75, alt. 1.0 mm. 



This minute species, which was first detected in the Tuscawaras 

 River near New Philadelphia, by Dr. V. ISterki, seems to have an 

 extended range. Examples have been seen from the following 

 localities: Alexandria, Va., ' Seneca, N. Y., Vermilion River, O., 

 Cuyahoga River and Garrettsville, O., and the Mississippi River, 

 Rockford, 111. Specimens from the Kankakee River, 111., and Iowa 

 City, la., though differing from the typical form in having the 



