NEW MARINE MOLLUSKS FROM THE WEST COAST OF 



AMERICA. 



By Paul Bartsch, 



AssiMant Curator, Division of MoUusks, U. S. National Museum. 



The present paper embraces diagnoses'' of new niollusks from the 

 Oreo-onian faunal area, belonging- to the genera Seila^ Bittimn., 

 Ceritldopsk^ and Metaxia. Figures of these will appear when the 

 monograph of these forms in course of preparation is published. 



SEILA MONTEREYENSIS, new species. 



Shell large, robust, brown. (Extreme apex lost in all our speci- 

 mens.) One of the cot^-pes has two and a half nuclear whorls remain- 

 ing. These are rather inflated, evenly rounded, marked by many 

 slender obliquely reti'active axial riblets. The transition of the nuclear 

 sculpture to the post-nuclear is very al>rupt. The sculpture of the 

 post-nuclear turn consists of three very strong, equal, and equall}^ 

 spaced lamellar spiral keels between the sutures. Channels separating 

 the spiral keels well rounded, a little widei' than the keels, crossed by 

 many subequal and subequally spaced slender ri])lets, of which about 

 40-50 appear on the whorls. Peripher}^ of tlie last whorl marked by a 

 fourth spiral keel not quite as strong as the keels of the spire and a little 

 more closely placed to the keel posterior to it than that is to its neighbor 

 above it. Base marked by a spiral keel which equals the peripheral 

 keel in strength, sepai'ated from it by a channel a little narrower than 

 the supraperipheral groove. Both of these channels are crossed by 

 the axial riblets. The remaining portion of the base slopes somewhat 

 concavel}" towaid the stout columella. Under the microscope the 



«In the preparation of the present diagnoses the following terminology is used: 

 Spiral sculpture, the markings following the direction of the coils of the whorls. 

 Axial sculpture, the markings which extend from the summit of the whorls toward 

 the umbilicus. 



The axial sculpture may be^ 



Vertical, when the markings are in general parallelism with the axis of the shell. 

 Protractive, when the markings slant forward from the preceding suture. 

 Retractive, when the markings slant backward from the suture. 



Proceedings U. S. National Museum, Vol. XXXIII— No. 1564. 

 Proc. N. M. vol. xxxiii— 07 12 177 



