181 CAI.IKOUNIA AiAKKMV Ol' SlUliNUKS. 



137. Zirphaea gabbii Tryun. 



/^irpAaa ^^addii Tr\ON, Proc. IMiil. Acad. Nat. Sci., 1S66. p. 144, I'l. I, I'ik . i. ('.Aiiif, Pal. Ca!., 

 Vol. II, pp. 52. SS, Pi. XV, fi)i. 10, 1869. Cooper, yih Ann. Re|)t. Cal. Si. .Min., 

 1SS8, p. 270. Dall, Trans. VVagner Inst. Sci., Vol. Ill, Part 4, 1S98, p. 81S. 



Zirphaa crispala (non Linn., Syst. Nat., Ed. X, p. 670, 1859) (Jide Dali.). Cpr., Bril. Assn. 

 Rcpt., 1863. p. 637. Keep, West Coast Shells, p. 210, tig. 179,1892. Williamson, 

 Proc. U. S. Nat. Miis., Vol. XV, 1892, p. 182. 



Shell of medium size, oblong, convex, thin; surface sculptured by concentric laminations, 

 which are much more elevated, and are provided with sharp, rasp-like teeth on the anterior half of 

 the shell; a slightly raiseil ridge. Hanked by two shallow depressions, runs obliquely posteriorly from 

 the umbo, divitling the spiny sculptured area iVom the concentrically ridged area; valve retle.\ed Irom 

 the umbones forward, covering the umbones; each valve is provided with a delicate spoon-shaped 

 tooth or process, which joins the shell just beneath the umbo. 



Dimensions. — Long. 72 mm.; alt. 35 mm.; diam. 30 mm. 



This species, tlioiigh closely allied to Z. cris2^ata, is pronounced a distinct species 

 by Dr. Dall. Speciinen.s identified by Dr. Dall. 



(^iiito rare in the npper 8ati Pedro .scries at San Pedro, Los Cerrito.s, Craw- 

 fish Uoorge's, and Dcadinan Island. 



Pleistocene. — Santa Barbara (Cooper): San Pedro (Cooper; Arnold). 



Miocene. — (?) Alanieda County (Cooper). 



Subfuiuily JOUANNETIN.E. 



Genus Pholadidea Goodall. 



Shell with a double anterior accessory plate (protoplax), the other plate present or absent, 

 the valves prolonged behind into leathery or testaceous cups or a tube (siphonoplax) (or the protec- 

 tion of the siphons. 



Type, Pholadidea loscomhiana Goodall. 



Subgenus Pholadidea s. .s. 



Shell with a double, rather small protoplax; the siphonoplax cup-like, the accessory ])lates 

 wanting; a single radial sulcus. 



Type, Pholadidea losco7iibiana Goodall. 



Section I'caiteUa V<dcncie'iincs. 

 Like Pholadidea, but with a small mesoplax, the two parts of the protojjlax confluent. 

 Type, Pholas penita Conrad. 



138. Pholadidea (Penitella) penita (Junrad. 



Pho/as penita CoN., Jour. Phil. Acad. Nat. Sci., Vol. VII, 1837, p. 237, PI. X\'III, fig. 7, 



-\-P. concamerala Desh., 1840, -\-P. C07iradi Val., 1846 {Jide Dall, Trans. Wagner 



Inst. Sci., Vol. Ill, Part 4, 1898, p. 819). 

 Parapholas penila CoN., Cpr., Proc. Zool. Soc, 1856, p. 210. 

 Pholadidea penita CoK., Cpr., Brit. Assn. Rept., 1863, p. 637. Cooper, 7th Ann. Rept. Cal. St. 



Min., 1888, p. 259. Keep, West Coast Shells, p. 212, fig. 181, 1892. Williamson, 



Proc. U. S. Nat. Mus., Vol. XV, 1892, p. 182. 

 Penitella penita Coii., Tryon, Proc. Phil. Acad. Nat. Sci., Monog. Pholad., 1861, p. 87. 

 Penitella spelwa Con. {ftde Gabb, Pal. Cal., Vol. II, p. 88, 1869). 



