424 MAZATLAN UNIVALVES 



sometimes not more than two and a half in the adult. A 

 ? variety has the sculpture much finer. A large sp. measures 

 long. *055, long. spir. *032, lat. '02,7, div. 25. 

 Hob. Mazatlan ; not common, off Spondylus and Chama ; 



Ifpool Col. 



Tablet 1982 contains 9 specimens in different stages. 



SECTION C. Species Chemnitziformes. 



513. CHEYSALLIDA CLATHEATTJLA, C. B. Ad. 



Chemnitzia clathratula, C. B. Ad. Pan. Shells, p. 165, 311, 

 no. 222. 



This species passes into the rounded cancellated forms of 

 Chemnitzia, (Subgenus Dunkeria,) from which it is known by 

 the distinct fold on the columella, and continuous peritreme. 

 The last whirl is but slightly contracted. It is known at 

 once from the rest of the Chrysallidse by its very elongated 

 form and rounded whirls. The solitary Mazatlan specimen has 

 lost its upper portion ; but the imperfection of the aperture 

 brings to light the oblique distinct columellar plait, which 

 escaped the notice of Prof. Adams. 

 Hob. Panama ; 10 sp. in sand ; (7. B. Adams. Mazatlan ; 



1 sp. off Chama ; L'pool Col. 



Tablet 1983 contains the specimen. 



514. CHEYSALLIDA CONVEXA, n. s. 



Chr. t. gracili, tereti, fenui, albidd ; vertice nucleoso anfr. ii. 

 helicoidalibus, magnis, declivibus, marginibus spira, parum 

 excurvatis, superantibus, qiiarum apex in anfr. normali primd 

 horizontaliterjacet, parum prominens ; anfr. normalibus v. valde 

 ' convexis, liris obtusis circiter xiv. radiantibus, ad suturam pro- 

 fundam scepius attingentibus, circa basin evanescqntibus ; lirulis 

 spiralibus in partem anteriorem anfractuum, interstitia tenue 

 decussantibus, quarum iii. in spird videntur, circa basin satis 

 rotundatam plures ; aperturd subovali, parum contracta ; 

 colwnella oblique plicata ; labio tenui. 



This remarkable shell has the apex and growth of a Chem- 

 nitzia, the convex whirls of Aclis, with the spiral plait and 

 (slightly contracted) aperture of Chrysallida. The lower half 



