iSTBOPO '-" l 



n.lnlm. 1 



<'\I:IN\ MIVIMK. ii. 



PI. Ml I \ I I 



Shell very small for the genus, the width of the aperture about 8 mm. in a 

 specimen having a length of r, mm. and a concavity of about 4. :t mm. Dorsumonly 

 moderately acute at tii-st and In-coming gradually quite obtuse. Surface with 

 several com ,\ strong lines or wrinkles of growth. 



of this species we have seen only the small specimen figured on plate IAII. 

 At tii-st we thought it might be an immature example of C. phnlrru, but a more 

 careful comparison proved conclusively that so great an expansion of the aperture 

 could not have occurred in the young of that species. Indeed, the expansion of the 

 aperture i<a sign of maturity in this genus, and that this condition has been reached 

 by the specimen in question i- further indicated by the strength of the lines of 

 growth which mark its surface where the latter is in good preservation. If these 

 indications are trustworthy then the species will be distinguished very readily from 

 all the others known of the genus by it- small size. 



Formation and locality. Hlack Klver group (Ctenodonta bed) near Cannon Falls, Minnesota. 

 Collection. B. O. riri.-i, 



* 



CAKINAROPSIS KXPLANATA, n. sp. (Ulricli.) 



PLATE I.XII. FIG. 5. 



Shell large, volutions apparently less than two, the first very small, the next 

 greatly expanded; hight only about one-third of the width; umbilicus very small; 

 dorsum angular. Aperture not well preserved, apparently transversely subelliptica), 

 and somewhat broadly sinuate in front; posterior lip little if at all reflected. Septum 

 large, curved inward, the inner edge about 18 mm. long in a specimen 38 mm. wide. 

 Surface of casts with obscure varices of growth. 



The width i- relatively greater than in any of the other species. The outer 

 surface of the septum is less deeply concave and its anterior edge farther within the 

 plane of the apertural margin than in ('. i-i/mlniln. which it resembles perhaps more 

 closely than the otb 



formation and loealil ; : . . K. -murky. 



CWfad*>M.-E. O. rirlch. 



