170 MAZATLAN UNIVALVES 
CLASS PTEROPODA. 
Omnia adhue ignota. 
CLASS GASTEROPODA. 
The knowledge of this class of Mollusks has rapidly inereas- 
ed since attention has been paid to their mouths and teeth. 
The main divisions here adopted are probably well founded. 
In the smaller sections we do not as yet know enough to 
stereotype an arrangement. Whatever character be taken as 
the “guide, families are united, unlike in other respects, or 
separated when many points of structure indicate affinity. The 
science being in a transition state from the old conchological 
arrangements, all dogmatism, on any side, is clearly out of place- 
Sus-cLtass OPISTHOBRANCHIATA. 
Orper TECTIBRANCHIATA. 
Famity CYLICHNID. 
Genus CYLICHNA, Loven. 
221. CyLIcHNA LUTICOLA, C. B. Ad. 
Bulla (Cylichna) luticola, C. B. Ad. Pan. Shells, p. 215, no- 
320: do. p. 319. 
Haminea luticola, H. § A. Ad. Gen. vol. 11. p. 16. 
Shell remarkably constricted in the middle, swelling an- 
teriorly. The surface is extremely finely decussated between 
the well-marked striz of growth. ong. ‘1, lat. 04. 
Heab—Panama ; crawling on liquid mud, near low water mark. 
at the bottom of a steep sand beach, rare; C. B. Adams.— 
Mazatlan ; 2 dead specimens off Chama; L’pool Col. 
Tablet 782 contains a characteristic specimen. 
