MAZATLAN UNIVALVES 217 



ffab Gallapagos Is., C timing. Mazatlan ; not uncommon, 



frequently growing on uneven surfaces, and often covered 



with algse ; L'pool Col. 



Tablet 1039 contains the two youngest specimens. 



Tablet 1040 contains 3 sp. smooth growth, hole oval. 1041, 

 3 do. regular form, hole with medial constriction. 1042, 3 do. 

 elongated growth. 1043, 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. 1047, 3 do. with medial con- 

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

 1049, 5 do. hol6 sub-linear, lobed in the middle. 



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

 to very coarse and unequal. 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 growth. 1055, 1 sp. with two large perforations 

 (made by PLithophagi.) 



274. FlSSUEELLA NIGEOCINCTA, n. S. 



" F. t. ovali, latd, conicd ; albd, lineis nigris radiantibus 

 eleganter picld ; striis radiantibus tenue ccelata ; aperturd 

 subcentrali, obscure trilobatd ; intus albd, margins tenue crenu- 

 lato, denticulis nigris ; callosilate alba, lined nigrd cinctd." 



"Differs from the young of F. alba in its greater breadth, 

 less compressed growth, finer striae and crenulations ; from F. 

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

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

 in the middle. L/ong. '75, lat. '52, alt. "3." 

 Proc. ZooL Soc. Dec. 1855. 

 Hab. Mazatlan, Mus. Gaming. ?Do. ; extremely rare, on 



Spondylus calcifer ; ISpool Col. 



Tablet 1058 contains one of two very young specimens '07 in 

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

 specimens in the Cumingian Collection. Although 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 , sp. ind. 



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

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

 trilobed ; colour green witjiin, nigropunctate at the margin ; 

 May 1856. v 



