MAZATLAN BIVALVES 109 



George's Port, N. Holland, (Peron). 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. 

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



extremely rare, from Chama and Spondylus ; L'pool 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 minusve trigonali, complanatd. concentrice striatd, 

 umbonibus acutis ; cardine dentibus minimis ; card. 1-2 conicis, 

 rotundatis ; lat. longis, gracilibus, vix monstrantibus ; fossa 

 ligamenti magnd, marginem attingente ; impress, muse, adduct. 

 magnis, subrotundatis. 



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 general habit. One is very trigonal, 

 Nucula-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 specimens are flat, concen- 

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

 within. A minute pair and fragments were also found, the 

 former measuring '03 across. 



The trigonal specimen measures long. '28, lat. '3, alt. '17. 

 The smallest one '19, '24, '11. 



Hab. Mazatlan ; nestling in Spondylus, extremely rare ; 

 L'pool Col. 



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



156. ? LASEA OBLONGA, n. s. 



L. t. obovali, transversd, incequilaterali, tumidiore, a it t ice 

 product'! ; alba, epidermide cinered, horridiore, subpilosd in- 

 dutd ; umbonibus prominentibus ; marginibus undique excurvis ; 

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

 menti parvd, appressd. 

 Dec. 1855. 



