ON SOME NEW CRETACEOUS (AND EOCENE?) MOL- 

 LUSCA OF CALIFORNIA. 



BY J. G. COOPER, M. D. 



[With Plates xlvii and xlviii.] 



I. Sistrum (Ricinula?) cretaceum n. sp. Plate xlvii, 

 figs, i and 2, twice natural size. 



Outline obtuse-rhomboid; higher than wide; first whorl 

 nearly flat, smooth, next two turbinate with about 20 nod- 

 ular strong ribs, crossed by 5 or 6 revolving ribs, the two 

 central strongest, and increasing to about 16 on the fourth 

 or body whorl; lip slightly expanded, with two spinous 

 projections on outer edge formed by the central ribs; 

 inner edge of labrum with three prominent teeth at irreg- 

 ular intervals, and columella with two close together, also 

 one on body-whorl near posterior angle of mouth; some 

 rudimentary teeth also near canal. A young specimen 

 has only four teeth, two on each side of mouth, distrib- 

 uted so as to form the angles of a square; as older ones 

 may develop more, the total dentation is still uncertain. 

 Canal very short, open ; spire shorter than mouth. Length 

 0.75 inch, breadth 0.62; mouth 0.50 long, 0.25 wide. 



This seems to be the first-species of Sistrum found in 

 North America, and is perhaps of the subgenus Ricinula, 

 though this depends on the question as to its being ma- 

 ture. All other species known live on the tropical Pacific 

 islands and in East Indian seas, a few also in the West 

 Indies and Brazil. Four specimens were received through 

 the State Mining Bureau from Morley, Shasta County, 

 with other known cretaceous species. The name Sistrum 

 is two years older than Ricinula, though used as a sub- 

 genus of the latter by Tryon and others. There is much 

 resemblance in this shell to young shells of Perissolax 

 brevirostris Gabb, but that has no teeth. 



1'itiH . Cal. Acad. Scr., 2d Ser., Vol. VI. August 18, 189C. 



