MAZATLAN BIVALVES 109 



George's Port, N. Holland, (JPeron). From its station in 

 crevices at extreme high water mark, it has probably often 

 escaped detection. It may hereafter be found to be one of the 

 very few ubiquitous species. The Mazatlan specimens were of 

 normal shape, '05 across. 



Hab. — Britain, Mediterranean, &c. : v. supra. — ? Mazatlan ; 

 extremely rare, fi'om Chama and Spondylus ; Upool Col. 



Tablet 495 contains the pair (broken in opening) and 2 

 opposite valves, probably belonging to each other. 



155. Lasea teigonalis, n. s. 



L. t. plus mimisve iriyonali, complanata, coitcentrice striata, 

 umhonihus acidis ; cardinc dentihus minimis ; card. 1-2 conicis, 

 rotund at IS ; lal. longis, grucilihus, vix moristrantibus ; fossa 

 ligamenti magna, marginem attingente ; impress, muse, addiict. 

 ?nagnis, suhrotundatis. 



Two specimens of this curious shell were found tightly 

 wedged in the hole of a borer in a Spondylus valve. They are 

 so different that they would be considered specifically distinct 

 but for their position and generaljiabit. One is very trigonal, 

 Nucyda-shaped, with a very projecting little conical tooth in 

 one valve fitting between two very small ones in the other. 

 The smaller specimen is of much more regular shape, with the 

 teeth scarcely discernible. Both sjjecimens are flat, concen- 

 trically striated, with a rough epidermis, and are rather pearly 

 within. A minute pair and fragments Avere also found, ihe 

 former measuring '03 across. 



The trigonal specimen measures long. '23, lat. "3, alt. '17. 

 The smallest one „ „ '19, „ 'SI; „ -11. 



Hab. — Mazatlan ; nestling in Spondylus, extremely rare ; 

 L'pool Col. 



Tablet 496 contains the tivo large pairs and one small valve. 



156. ? Lasea obloxga, w. s. 



L. t. obovali, transversa, i?icequilaferali, tumidiore, antice 

 productd; alba, epidermide cinered, horridiore, subpilosd in- 

 dutd ; umbonibus prominentibus ; margitiibus undiqne excurvis .- 

 dent. card, una, minuto, conico, lat. gracillimis ; fossa liga- 

 mentt 2Jarvd, ap2n'essd. 



Dec, 1855, • ^ 



