mazatlan bivalves 631 



[Family TELLINID^.] 

 686* Tellina , sp. ind. (c.) 



Tablet 2521 contains two valves, in form resembling T. dona- 

 cilla; but with external concentric sculpture continuous instead 

 of alternating. The young shell is extremely thin, with the 

 sculpture in sharp ridges, rosy ; the larger is very thick for its 

 size, yellowish, with the ridges broad and rounded. It is proba- 

 ble that they belong to different species. Inside with a strong 

 bifid tooth between two pits ; lateral teeth none. 

 J5a6.— Mazatlan ; extremely rare, off Spondylus ; L'pool Col. 



[Family CAEDIAD^.] 



687. Caedittm eotundatum, n. s. 



C. t. parvd, cBquilaterali, ventricosd, alha ; costibus circifer 

 xxii. acutis, vix granosis, quarum ventrales circiterym.. majores ; 

 interstitiis latis, planatis, vix decussatis ; dent. lat. hand dis- 

 tantibus. 



Of this beautiful little shell two opposite valves were found, 

 apparently belonging to each other. It resembles C. alabas- 

 trum, but with more numerous and less conspicuous ribs. 

 Long. -063, lafmb. 

 JBaJ.— Mazatlan : extremely rare, off Spondylus ; L'pool Col. 



Tablet 2522 contains the two valves. » 



[Family KELLIAD^.] 



688. Lasea , sp. ind. 



Tablet 2523 contains the hinge portion of a shell in shape 

 somewhat like Mactra stultorum ; with most minute and 

 crowded concentric strise on the epidermis ; inside with two 

 slender lateral teeth, and a hinge pit near the umbo under one 

 of them. 

 Hob. — Mazatlan ; 1 sp. in Spondylus ; L'pool Col. 



694. P MONTACUTA chalcedonica, n. s. 



?M. t. tenuissimd, inter dum opacA, interdum diaphand, cos- 

 taned : ovali, marginibus regulariter excurvatis, umbone pro- 



• No. 685 is Tyleria fragilis, R, ^ A. Ad, 



