Hyatt.] 328 April 4, 



[Prionocerae.] 



Prionoceras, 1 nobis, includes species with broad, acute, straight- 

 sided, undivided, ventral lobes similar in outline to the first pair 

 of saddles, and the first pair of lobes. The magnosellarian sad- 

 dles are undivided. The young of these shells, if they had the 

 same mode of development as other Goniatites must have had 

 more rounded first pair of saddles at some stage of growth, and 

 this would render the sutures at this stage similar to those of 

 some forms of Parodiceras. The immediate affinities, however, 

 connect them with Brancoceras, from which genus we should not 

 have dared to separate Prionoceras, but for the artificial necessity 

 of showing clearly the genetic relations of this genus and Glyphio- 

 ceras. The species differ from Brancoceras only in the acutenoss 

 of the first pairs of saddles and lobes, and their peculiar pyramidal 

 shape. The type is Pri. (Gon.) divisum Munst. Ueber Clym. et 

 Gon. pi. 4, fig. 6, of the Devonian. This species and Pri. Belvalia- 

 num, De Kon. Anim. Foss. pi. 49, fig. 5, and Calc. Carb. pi. 50, figs. 

 8-10, have sutures similar, in their undivided ventral lobes, and 

 lateral outlines, but the first pair of saddles on the venter are 

 pyramidal in shape, like those of Glyphioceras, and are evidently 

 transitions to this last genus. 



Grlyphioceras, 2 nobis, includes species with whorls in section 

 semilunar, trapezoidal or compressed, the abdomens broad and 

 convex, the sides divergent outwardly, and frequently costated. 

 The sutures are remarkable for the acute, angular outlines of the 

 lobes and saddles in the adolescent and adult stages, and 

 the large size and frequently bottle-shaped siphonal saddle. 

 There are exceptions to the angularity of the lobes in some spec- 

 ies, which retain the early larval form of the outlines of the sut- 

 ures in their later stages of growth, but in these, the rapidly nar- 

 rowing ventral lobes, and the large size of the linguiform first 

 lateral saddles enables one to refer the species to their proper 

 genus. In their later larval stages the sutures are not distinguish- 

 able from those of Munsteroceras, with which also the forms of 

 the whorl agree equally closely. The siphonal saddles are small, 

 and occupy only the apex of the straight-sided, deep ventral lobes, 

 and the first pair of saddles are spatulate, and the lateral lobes 

 and magnosellarian saddles are precisely as in that genus. 



1 Houov, a saw. * rA,v<JHS, the uotch in an arrow. 



