358 MAZATLAN TJNITALYES 



Tablet 1706 contains a series of 11 specimens of different 

 ages, beginning from '027 by '018, and presenting the extremes 

 of variation. 1707, 2 sp. alabastrine variety, and as a contrast, 

 one with black incrustation ; also 2 fragments to illustrate the 

 adolescent and the adult basal sculpture. 



GENUS EISSOA, Freminville. 



Bull. Soc. PMlom. 1814, p. 7. 



Loxostoma, Bivon. 1832. LamareMa, Leach. G-onostoma, 

 MWf. 



411. ? ElSSOA L1RATA, n. S. 



? R. t. conoided, albido-fuscd, solidiore ; anfr. vi., quorum ii. 

 primi tumidiores, Icevi ; reliqui planati, eleganter lirati, liris 

 plurimis (in spird circiter x .) extantibus, interstitiis cequantibus, 

 quadratis ; sulco latiore circa peripkeriam, suturam super ante ; 

 anfr. radiatim obsolete undatis, prope suturam subnodosis ; 

 marginibus spirce excurvatis ; basi subangulato ; aperturd sub- 

 ovali, peritremati continuo ; labro antice expanse : operculo 

 solidiore, corneo, rufo-fusco, semilunato, convexo ; elemenlis con- 

 centricis ; nucleo subcentrali, marginem interior em versus ; intus 

 processu conico anteriori prcelongo, extante, costd ad alterum 

 marginem decurrente. 



Of this beautiful shell one perfect specimen was found with 

 its operculum. This makes its generic position doubtful ; as 

 it presents the concentric elements of Jeffreysia and the 

 anteriorly projecting process of Bissoina, in conjunction with 

 a shell typically Rissoid. The nucleus is projecting, and 

 situated about half way between the centre and the inner 

 margin. It appears that the entire sculptured layer may be 

 abraded ; for a specimen was found (which but for one in an 

 intermediate state would surely have been regarded as a dis- 

 tinct species) without either lirse or transverse waves, and 

 scarcely shewing the sutural furrow ; but with a smooth surface 

 most delicately corrugated transversely. Long. '12, long, 

 spir. '073, lat. '063, div. 25. 



Hob. Mazatlan ; 9 sp, off Chama and Spondylus ; L'pool Col. 

 Tablet 1708 contains the perfect and the abraded specimens. 



