9tA PALAEONTOLOGY OF NEW- YORK. 



i 

 _ nent nmbo. The hinge-plate is extended in -gradually converging vertical lamcllaD which 



are joined to the shell throughout their length, while the crura are extended into the 



cavity in thin free lamellae. Genus Anasteophia,* of which Pentamerus terneuilii, 



P. interplicata and P. reversus are types. 



7. Forms elongate, not lobed. Ventral valve with connected dental lamellae, forming a 



trough supported on a septum. Dorsal valve with free crura : no area. Shell-structure 



punctate. Genus Amphioenia : Type Petvtamertu elongatus 4Vanuxkm ) =: A. 



elongata. 



These modificatious of a tj'pe, of which, until recently, but two genera have 

 been recognized, are well marked in nature, and they seem to me to demand some 

 farther recognition than that of subordination to the Family Eiiynciionellid.T':. I 

 shall therefore propose the Family Pentasierid.I': to include the genera above 

 enumerated, as well as the Genus Camakophokia, and probably Triplesia and 

 some of the species of Camarella,! and' perhaps also the Genus Gypidia of D al- 

 mas, making G. conchydium the type.J In this arrangement, it appears to mc that 

 Ave have a well-marked family of Braciiioi'Oda which has existed from the earliest 

 palteozoic epoch, and has continued throughout the entire series to its close. 



• I am aware that Mr. Sraler, of the Museum of Comparative Zoology at Cambridge, in a Bulle- 

 tin of that Institution, has proposed the name Bkaciiymercs for these forms ; but since that name is 

 preocciipied for a genus of Coleoptera, it cannot be adopted in this relation; and my own determi- 

 nation of the generic distinction of these forms having been made long since, I shall adopt the name 

 proposed above. 



t I cannot recognize the rhynchonelloid typical species of Caharella as congeneric with many of 

 those more recently placed under that genus by its author. 



X In the revision of the Pbntambrid^, I am by no means sure that the Genus Gtpidia will not be 

 recognized. I have under consideration at the present time an American species of similar external 

 character, presenting certain modifications of the hinge-plate in the dorsal valve, which will require a 

 distinct designation. • 



