194 REPORT ON THE STATE CABINET. 



fera), and forming no vertical lamellse. P. liratiis and P. microcamerus 

 are European forms of this type = the Genus Stricklandinia of Billings ; 

 of which *S'. canadensis, S. brevis, S. gaspensis and >S'. anticostensis are charac- 

 teristic forms. 



5. Short gibbous or ventricose forms ; the ventral valve much the 

 larger, with or without mesial fold, a large fissure, and elongate much 

 incurved trough-shaped pit. Dorsal valve depressed in front : an area on 

 both valves ; that of the ventral valve striate as in Spirifera ; lamellae 

 of dorsal valve separate and diverging. Genus Gypidula, of which G. 

 (P.) occidentalis and G. Iwviusculus are types. 



6. Rotund or gibbous forms, with the valves, as in ordinary Penta- 

 MERUS, reversed. The ventral valve is the smaller, gibbous in its upper 

 part, depressed or sinuate below, with the V-shaped pit sessile for nearly 

 its entire length ; a small flattened space on each side of the fissure. The 

 dorsal valve is ventricose, larger than the ventral, with prominent umbo. 

 The hinge-plate is extended in gradually converging vertical lanaellse 

 which are joined to the shell throughout their length, while the crura 

 are extended into the cavity in thin free lamellae. Genus Anastrophia,* 

 of which Pentamems verneuili, P. interplicatus and P. reversiis are types. 



7. Forms elongate, not lobed. Ventral valve Avith connected dental 

 lamellae, forming a trough supported on a septum. Dorsal valve with 

 free crura : no area. Shell-structure punctate. Genus Amphigenia : type 

 Pentamems elonc/atus (Vanuxem) = Amphigenia elongata. 



These modifications of a type, 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 Rhynchonellid^. I shall therefore propose the Family Penta- 

 MERiD^ to include the genera above enumerated, as well as the Genus 

 Camarophoria, and probably Triplesia and some of the species of 

 Camarella,! and perhaps also the Genus Gypidia of Dalman, making 

 G. conchgdiimi the type.J In this arrangement, it appears to me that we 



* I am aware that Mr. Shaler, of the Museum of Comparative Zoology at Cambridge, in a 

 Bulletin of that Institution, has proposed the name Brachtmerus for these forms; but since that 

 name is preoccupied for a genus of Coleoptera, it cannot be adopted in this relation ; and my 

 own determmation of the generic distinction of these forms having been made long since, I shall 

 adopt the name proposed above. 



1 1 cannot recognize the rhynchonelloid typical species of Camarella as congeneric with many 

 of those more recently placed under that genus by its author. 



% In the revision of the Pentamerid.1:, 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 



