I'LIOCENE PECTENS. 109 



1S.S7. fl'ectcn liaslatuf! Sowerby, Whiteaves, Trans. Koy. tSuc. Canada, vol. 4, sec. 4, 18S7, p. 119. 

 1S98. Pecten hastatus Sowerby, Dall, Trans. Wagner Free Inst. .St-i., vol, :!, pt. 4, 1898, p. 708. 



1903. Pecten [Chlamys) hatitahtii Sowerby, Arnold, Mem. Cal. .'Vcad. Sci., vol. :>, 1903, ji. 109, [>\. 11, 



figs. 4, 4a. 



1904. Pecten hastalux Sowerby, Keep. West. Am. Shells, ]i. 40. 



Di'.scr/pt/'ov. — yiioll averaging- ulxnit 6-i iiiilliinetcvs in altitude, slightly .shorter 

 than high, inequivalve. equilateral (exeept for ears), compressed and with serrate 

 margins; base evenl_y rounded below; sides slightlj- concave above. Right valve 

 with 9 pairs of narrow, elevated, spiny ribs, along the sides of which are a pair 

 of smaller spiny riblets; major interspaces much wider than ribs, concave-l)ottomed 

 and ornamented by 1 or 3 thread-like, spiny, intercalary ri))lets; whole surface 

 sculptured by microscopic im))ricating lines, of which th(> sjjines on the ribs and 

 riblets are only moditications; hinge line equal to one-half length of disk; ears 

 unequal, the anterior being about two and one-half times the length of the 

 posterior: anterior ear w^ith 7 or 8 prominently spiny radials and minor riblets, 

 and imbricating incremental lines; byssal notch deep and almost as wide as ear; 

 posterior ear small, and sculptured by tine, spiny I'adials and imliricating incremental 

 lines. Left val\e with about 1» narrow, very prominently spiny ribs; interspaces 

 wide, concave-bottomed, and ornamented by a single prominent, central, imbricated 

 riblet, on each side of which are minor thread-like riblets; whole surface of disk 

 with fine incremental sculpture as in right valve; ears similar to those of right 

 valve except that the anterior one has more I'ibs and riblets and no byssal notch. 

 Hinge with almost obsolete cardinal crura. Color, golden yellow to pink, the left 

 valve being the darker. 



Dimensions. — Alt. tli mm.; long. (i2 mm.; hinge line :U mm.; diameter 23 mm. 



This beautiful species, which is the southern representative of the group of 

 which var. Jtericius is the normal form, is characterized by the great prominence 

 of the spines which adorn the major ribs of both valves. A fossil specimen of 

 this species from the l)ryozoan Pliocene marl of Santa Rarl)ara served as Conrad's 

 type of P. alt!j>l!n(tu.s. (See PI. XLI, tig. 4.) 



A variety of /'. ii((sfiifi(s, found associated with th(> typical form in the 

 Pliocene at San Pedro. Santa Barl:)ara. and San Diego, has the strongly indi\id- 

 ualized ril)s which characterize the type, l)ut almost completely lacks the prominent 

 spines. The young of this smooth form, and also of the typical spiny form, uj) 

 to an altitude of about 15 millimeters are indistinguishable from the young of 

 [{in n Ifi's gigan taix. 



Whiteaves reports /*. liastatus from Quatsino Sound, British Colum})ia. In 

 describing his specimens, which were collected by Doctor Dawson, he mentions 

 the few prominent ribs with a single row of high spines which characterize this 

 species. 



R.\N'GE. 



Living. Quatsino Sound, British Columbia (Dawson, Whiteaves); jMonterey (But- 

 ton); San Pedro (Oldroyd, Raymond); Catalina Island (Arnold); San Dieg-o 

 (Raymond). (In all cases dredged.) 



Pleistocene (lower San Pedro formation). Bath-house Beach, Santa Barbaia; 

 Deadman Island, San Pedro (Arnold). 



