312 t"ALIFOKNIA ACADEMY OF SCIENCES. 



350. Hipponyx antiquatus Linmrus. 



Patflla antiquatus 1,inn., Syst. Nat., Kd. XII, p. 1259, 1768. DiLLW., p. 1035, No. 44, 1760. 



Hipponyx anlujuatuslAH'^i., Menkk, Zeit. f. Mai., p. 79, 1853. CPR., Proc. Zool. Soc, 1.H56, p. 3; 

 Brit. Assn. Rept., 1863, p. 654. Tryon, Man. Conch., Vol. VIII, p. 134, PI. XL, 

 fiRS- 93-99. '8.S6. Cooper, 7tli Ann. Rcpt. Cal. St. Min., 18S8, p. 244. Keep, 

 West Coast S1k-11.s, p. 74, fig. 59, 1892. 



Concholepas antiquatus LiNN., H. & A. Adams, Gen. Rec. Moll., Vol. I, p. 373, 1853. 



Shell oljliquely conical; ape.\ blunt, projecting beyond posterior marj^in of shell; surface 

 roughened by prominent lamellar, concentric lines of growth; base ovate; rim smooth, not crcnated. 



This is a very v.ariable species, the specimen descrilictl liaving ;ui iiiHiisuall}' 

 elevated apex. The specimen was identified by Dr. Dall. 



Carpenter believe.s tlie ITipponijK milrula of the West Indian fauna to be 

 identioal with the f/ippnnij.c antiquntvx of the Pacific Panama ro<;ion. Tf the.-^e two 

 are identical it is another case of an old species which has lived on in both habitats, 

 having changed but little since the two regions were connected by water; or else it 

 is a case of parallel development, where two species, having come from a common 

 stock and living among like conditions, though .separated geographically, have 

 developed along parallel lines and are enough alike at the present time to warrant 

 their being called the same species. In such a genus as Hippowjx, where there are 

 so many mutations in a single species, either case would be pcssible. 



One specimen from the lower San Pedro series of Deadmau Island; also found 

 in the Pliocene of Deadman Island. 



Licing. — Bodega .Bay and south; South America; Atlantic (Cooper). 



Pleistocene- — San Pedro (Cooper; Arnold). 



351. Hipponyx cranioides Carpenter. 



Hipponyx crajiioides Cpr., Ann. & Mag. Nat. Hist., 3rd Ser., Vol. XIII, 1863. p. 428. Tryon, 

 Man. Conch., Vol. VIII, p. 135, PI. XL, figs. 6, 7, 18S6. Cooper, 7th Ann. Rept. 

 Cal St. Min., 1888, p. 244. 



Shell obliquely conical, depressed; apex inconspicuous, blunt, posterior to center, but not 

 reaching margin; surface ornamented with several wide lamella- of growth which are grooved by 

 numerous radiating furrows; aperture ovate; rim thin, sometimes corrugated near outer edge; 

 interior smooth. 



Dimensions. — Long. 19 mm.; lat. 17 mm.; alt. 6 mm. 



Distinguishable from 77. nniiquatus by depressed shell, more central apex, 

 and more regular lamellie of growth, which are prominently radially furrowed. The 

 specimen described was identified by Dr. Dall. 



According to Tryon //. tumens equals H. cranioides. 



Rather common in the lower San Pedro series at Deadman Island and San 

 Pedro; rare in upper San Pedro serie.s at Deadman Island and LosCerritos. Found 

 also in the Pleistocene at Spanish Bight, San Diego. 



Living. — Straits of Fuca to Santa Barbara (Cooper). 



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



