MAZATLAN UNIVALVES 217 



Sa&.— Gallapagos Is., CWii/if/.— Mazatlau ; not uncommon, 



frequently growing on uneven surfaces, and often covered 



with alg?e ; L'pool Col. 



Tablet 1039 contains the two youngest specimens. 



Tablet 1040 contains 3 sp. smooth growth, hole oval. — 1011, 

 3 do. regular form, hole with medial constriction. — 104)2, 3 do. 

 elongated growtli. — 1013. 2 do. hole trilobed. — 1044, 1 do. hole 

 elongated, lobed at each end. 



Tablet 1045 contains 3 sp. rough growth, hole rounded oval. — 

 1046, 3 do. hole elongated oval. — 10i7, 3 do. with medial con- 

 striction. — 1048, 4 do. hole elongated, obscurely trilobed. — 

 104.9, 5 do. hole sub-linear, lobed in the middle. 



Tablet 1050 contains 5 sp. ribs varying from fine and equal 

 to very coarse and imequal. — 1051, 3 sp. red colour developed 

 outside. — 1052, 7 sp. with more or less of red stains within. — 

 1053, 2 sp. dark line round callus well developed. — 1054, 2 sp. 

 elevated gro-n-th. — 1055, 1 sp. with two large perforations 

 (made by FLithojihagi.) 



274. FlSSUEELLA NIGEOCINCTA, 71. S. 



"F. t. ovali, lata, conicd ; albd, lineis nigris radiantihus 

 eleganter pictd ; striis radiantihus temie ccelata ; aperturd 

 suhcentrali, obscure trilobatd ; intus albd, margine tenue crenu- 

 lato, denticulis nigris ; callositate albd, lined nigra cinctd." 



"Differs fi-ora the j'oung of F. alba in its greater breadth, 

 less compressed growth, finer stria? and crenulations ; from F. 

 nigropunctata, in the black line round the callosity ; and from 

 both in the form of the hole, wliich is trilobed, not contracted 

 in the middle. Long. "75, lat. '52, alt. "3." 

 Proc. Zool. Sac. Dec. 1855. 

 Hah. — Mazatlan, Mus. Cuming. — ?Do. ; extremely rare, on 



Spondylus calcifer ; L'pool Col. 



Tablet 1056 contains one of two very young specimens '07 in 

 length, which may belong to the above species, described from 

 specimens in the Cumingian Collection. ^Uthough so small, it 

 displays no trace of spiral vertex. Shell white, with black 

 stripes. Hole suboval : this may be a character of youth. 



275. FissuEELLA , .92;. ind. 



ShcU elongated, conic, much compressed ; ribbed as in F. 

 virescens, &c. ; anterior side shortened ; hole long, narrow, 

 trilobed ; colour green within, nigropunctate at the margin ; 

 Ma?/ 1856. V 



