276 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



larly tapering upward, and has a much narrower aperture, and a proportion- 

 ally wider coil of involuted body-turns. 



The only specimen of this shell yet seen has the thin, reflexed, inner lip 

 closely appressed below, where it is wider than represented in our figure 2, b, 

 and shows, in certain lights, a very obscure, oblique ridge, not seen in the 

 figure. Unfortunately, the lip is broken away, so as to leave some doubts in 

 regard to the true nature of the ridge ; but, from what can be seen, I am 

 induced to refer the species doubtfully to the genus Cylichna. It is a thinner 

 shell, however, and less cylindrical in form than the species of that germs 

 usually are. If not a Cylichna, however, it should possibly be called Ha- 

 minea, or Atys (Roxania) volraria, as its thin shell and other characters would 

 seem to indicate relations to these genei'a. 



Locality and posit t o n. — Moreau River; from the Fox Hills group of the 

 Upper Missouri Cretaceous series. 



Cylichna scitula, M. & H. 



Plate 31, figs. 3, a, b. 

 Ciilichna scitula, Meek and Hayden (1660), Proceed. Acad. Nat. Sri. Philad., XII, 178. 



Shell small, rather solid, nariFOW-subellipfcical, approaching subcylin- 

 drical ; summit truncated, and occupied by a comparatively large umbilicoid 

 depression; aperture very narrow, arcuate, widening little below; umbilical 

 region slightly impressed ; inner lip reflexed and twisted, so as to form a 

 small indistinct -fold at its base:* surface marked by fine, obscure lines of 

 growth, which are crossed by impressed transverse striae, separated by spaces 

 about two or three times their own breadth near the middle of the outer 

 whorl, but becoming much more closely crowded toward the extremities. 



Length, 0.24 inch; breadth, 0.14 inch; widest part of aperture, C. 07 

 inch; breadth of same near upper extremity, only 0.02 inch. 



At a first glance, this little shell might be mistaken for the young of our 

 C. volvaria ; but, on comparison, they will be found to differ essentially in sev- 

 eral respects. In the first place, the summit of the species now before us is 

 truncated, and lias a larger umbilicoid impression ; while that of C. volvaria is 

 tapering, narrowly round, and provided with a very small impression. The 

 aperture of 1 he latter is also comparatively broader below, its sides less con- 



*This character is not well shown iu fig. 3, «, which also makes the base of the aperture much too 

 angular, and the summit of the shell too narrow. 



