170 MAZATLAN UNIVALVES 



CLASS PTEROPODA. 

 Omnia adhuc ignota. 



CLASS GASTEROPODA. 



Tlie knowledge of this class of Mollusks has rapidly increas- 

 ed since attention has been paid to their mouths and teeth. 

 The main divisions here adopted are probably well foimded. 

 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 afiinity. Th» 

 science being in a transition state from the old conch ological 

 arrangements, all dogmatism, on anj' side, is clearly out of piace. 



Sub-class OPISTHOBR^INCHIATA. 



Oedee TECTIBEANCHIATA. 



Family CYLICHNID,/E. 

 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. Sf A. Ad. Gen. vol. ii. p. 16. 



Shell remarkably constricted in the middle, swelling an- 

 teriorly. The surface is extremely finely decussated between 

 the weU-marked stria; of gr«wth. Long. '1, lat. "04. 



Hah. — 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 783 contains a characteristic specimen. 



