334 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



smooth, though this may he partly due to accidental erosion before the shells 

 were embedded in the matrix. 



It is with considerable hesitation that I have concluded to remove this 

 species to the genus Mesalia ; none of the specimens being in a condition to 

 show the base of its aperture. Consequently, I have been unable to deter- 

 mine whether or not its lower margin is produced and notched, or subcana- 

 liculated, as in that genus. From its rounded body-volution, and the deep 

 sinuosity of its outer lip (as shown by the curve of its lines of growth), as 

 well as its general resemblance to some of the species of that group, how- 

 ever, I have been led to think it may probably be a Mesalia. 



Locality and position. — Twelve miles southwest of Salina, Kansas; 

 Dakota group of the Upper Missouri Cretaceous. Prof. B. F. Mudge, col- 

 lector. 



CERITHIOPSIDiE. 



Genus CERITHIOPSIS, Forbes and Hanley. 



Synon. — Cerithium (sp.) of some earlier authors. 



CerifMopsis, Forbes and Hanley (1849), Brit. Moll., Ill, 364.— H. and A. Adams (185?), Genera, 



Recent Moll.. I, 240.— Chenu (1859), Man. Conch., I, 231.— Gabb (1864), Palieont. 



Cal., I, 116; lb., II, 114.— Stoliczka (1868), Palaeont. Indica, II, 185.— Gould and 



Binney (1870), Iuvert. Mass. (2d ed.), 385. 

 Alaba, H. and A. Adams (1853), Genera Recent Moll., I, 241 (as a subgenus). 

 Sella, A. Adams (1861), Anu. Mag. Nat. Hist., VII (3d ser.), 131 (as a subgenus). 



Etym. — Cerithium; irjuc, form. 

 Type. — Murex tubercxtlaris, Mont. 



Shell small, turriculated, many-whorled, dextral, marked with revolving 

 rows of granules, or small ridges, sometimes cancellated, smooth, or with a 

 few irregular varices ; aperture more or less rounded, or subquadrate, ante- 

 riorly sinuate, with a small, short, oblique canal, or merely emarginate; outer 

 lip acute, arcuate, and a little produced anteriorly ; inner lip reflected and 

 rather broad. 



H. and A. Adams, in their joint work on the recent Mollusca, separated 

 the species belonging to this genus into two subgenera; and subsequently 

 one of those authors added another. These sections may be severally distin- 

 guished as follows : 



1. cerithiopsis, Forbes and Hanley (typical). 



Shell with surface granular, cancellated, or with revolving ridges; 

 aperture sinuated, and having a short canal anteriorly. — (Type as 

 above stated.) 



