152 MAZATLAN BIVALVES 



fry. It probably resembles P. costellata, Conr. from the 

 Sandwich Is., but that is described as having both beaks alike. 

 The smallest specimen is '05 in length ; the largest, long, (the 

 diagonal of the lozenge) 1*12, lat. '68, alt. '17. 

 Hob. Mazatlan ; on I. Chemnitzii and Spondylus calcifer, 



extremely rare : L'pool Col. 



Tablet 689 contains 1 pair and 2 valves, very young. 690, 

 the most characteristic specimen, in situ. 



FAMILY 

 GENUS PECTEN, Mull. 



Of this (in most places) abundant genus only 3 very small 

 valves were found. The neighbouring genus Lima was alto- 

 gether absent. 



207. PECTEN CIBCULAEIS, Sow. 



Proc. Zool. Soc. 1835, p. 110. Hani. Descr. Cat. p. 271. 



Dull ash, variegated with chocolate ; ears very large ; inter- 

 stices near the umbo finely decussated. The opposite valves 

 differ in sculpture. Long. *28, lat. '26, alt. '12. 

 JZ#6. Guaymas ; in sandy mud, 7 fm. ; Col. Chiming. St. 



Vincent's [?] Hanley. Mazatlan ; extremely rare : L'pool 



Col. 



Tablet 691 contains the only valve I found. 



FAMILY SPONDYLID^E. 

 GENUS SPONDYLUS, Linn. 



~ 208. SPONDYLUS CALCIFEE, n. s. 



S. t. maxima, ponderosd, solidd, plerumque orbiculari ; rubro- 

 purpureo ; valvd superiors cos t is minimis aculeatis 

 creherrimis tectd, hue et illuc costis irregularibns squamosis ; 

 squamis curtis, ad basim arcuatis, suprafoliatis ; valvd infer- 

 iore plerumque foliates ; area ligamenti magnd, ligament o hand 

 tecto ; intus subnacred, limbo lato toto pur pure o , seu 

 nonnumquam flavesco-rubente ; margine extremo ere- 

 berrime et minute crenulato; dentibus validis ; fossa 

 ligamenti canalibus 2-6 parallelis t decussatis ; musv. imp. sub" 

 orbiculari^ magnd. 



