Tss'f '] PROCEEDINGS OF THE NATIONAL MUSEUM. 265 



flated subceutral with the color deeper than oil the rest of the shell- 

 sculpture of One very numerous radiating grooves with broader flat in- 

 terspaces or flattened riblets, crossed by flue concentric, slightly irreg- 

 ular narrow ridges made more prominent by the slightly projecting 

 epidermis; on the posterior sixth of the shell the radiating riblets are 

 coarser and slightly rounded, crossed by rather distant more elevated 

 concentric laminae fringed with epidermis; the posterior area separated 

 from the rest of the surface by a slightly elevated somewhat curved 

 radial lamina which is minutely frilled or puckered in such a way that 

 its edge where unbroken is delicately notched. Posteriorly the shell 

 gapes a little; the anterior margin is evenly rounded, below evenly 

 arched, posteriorly subtruncate and everywhere simple and sharp ; the 

 cardinal margin is reflected and elevated before the umbo, more depressed 

 behind it with a delicate ligamentary insertion plate; there are no lat- 

 eral teeth in either valve ; in the right valve the inner edge of the hinge- 

 plate is continued as an elevated line above which the upper posterior 

 margin is produced vertically, making this valve a trifle larger than 

 the other, and more angular at the upper end of the truncation ; in 

 the right valve are two slender curved cardinal teeth, the longer 

 notched near its tip, in the left valve a single tooth excavated above. 

 Longitude of shell 29 ; altitude 25 ; maximum diameter 20 mm . 



Hab. — Coast of Lower California at Station 2828 in north latitude 

 24° 11' and west longitude 109° 55' in 10 fathoms; fragments were col- 

 lected at Stations 2823 and 282G, in 8 to 27 fathoms, shelly bottom, 

 within a few miles of the preceding and also in material dredged near 

 San Clemente Island in 25 fathoms. 



The soft parts of this species resemble those of other Cardiuras, ex- 

 cept that the siphonal septum is produced forward to and around the 

 foot, completely separating the anal and branchial chambers. This 

 septum is thin, membranous, and imperforate except for the foot. The 

 siphonal orifices are profusely papillose and most of the soft parts are 

 of a pinkish color. 



This shell differs from all other Cardiums, recent or fossil (except C. 

 Cuming I), in the total absence of lateral teeth The section Lophocar- 

 dium of Fischer was based on the prominent radial lamina of G. Cum- 

 ingi, but an examination made at the British Museum by the courtesy 

 of Mr. E. A. Smitb, at my request, showed that that species partakes 

 of the same hinge characters. For this reason I raised the section to 

 the rank of a subgenus under Dr. Fischer's name. 



From C. Cumingi, which was obtained from the same region, the 

 present species differs in form, in details of sculpture, and in the less 

 elevated radial lamina. It is one of the most beautiful shells of the 

 genus, but so fragile that it is extraordinary that even a single speci- 

 men was obtained in a perfect state. 



Tbe soft parts resemble in the main those of other Cardiums except 

 in regard to the siphonal septum. A partial siphonal septum is com- 



