58 CARBONIFEROUS AMMONOIDS OF AMERICA. 



phylum or snperfivmily, and derives them from a different Devonian t^enus, 

 Tornoccras. This seems to tlie writer to he goiny further than the facts 

 warrant. Ikit it is beyond (h>nbt that the (Tlyphioceratida!, as Hyatt used 

 the term, can be divided into two series. The writer prefers to retain the 

 two under the same phylum or superfamily, (llypliioceratida;, and to 

 name each of the component series or families after the most character i.stic 

 genus. 



Under the Glyphioceratidse s. str. would fall I'rionoceras f, J'ericycJus, 

 Gh/phioceras, Goniatites, Gastrioceras, Parahfjoceras, ScIi istocrras. 



Under the Aganididfie would fnll Af/anidcs, Muensteroccras, Gonioloho- 

 ceras, Dhiiorphocpras, MiUeroccras. 



From the Grlyphioceratid;v it apj)ears that the Arcestidu' iind the Tro- 

 pitida2 have been derived. The Ptychitidse seem to have sjn'ung from the 

 Agauididaj. 



Family GLYPHIOCERATID.E s. str. 



Genus I'kkinoceras ? Plyalt. 



This genus was established Vjy Hyatt" to include rather evolute, low- 

 whorled forms, with undivided external loljes,- and angular Inlx's and 

 saddles. The type chosen was Goniatites divisus Muenster of the Devonian. 

 Another species assigned to the genus is Goniatites hclratlatnis de Koninck 

 from the Lower Carboniferous. It is very doubtful if eitliei- species fits the 

 description. Certainly neither has angular saddles, and even the external 

 lobe of Goniatites hclvalinims is divided at maturit)'. 



As a consequence of this the genus has been either abandoned entireh' 

 or merged by most authors with Aganides (Brancoceras). Whether this be 

 correct or not, the ontogeny of later forms teaches that sucli a genus was 

 the radicle of the greater part of the Glyphioceratida?. It is very doubtful 

 whether I'rionoceras is represented in America at all, but three species are 

 doubtfully assigned to it. Freeh'' has shown that Goniatites divisus, the 

 type of I'rionoceras, is identical with Goniatites sulcatus Muenster and 

 G. linearis Muenster, l)otli listed by Hyatt as most characteristic members 

 oi' Brancoceras (^Aganides). A strict ruling would thus throw this genus out 

 entirely, although Haug projxises to retiiin it on ;iccount of its sup])osedly 

 longer body chamber. 



" Proc. Boston Soc. A'at. Hist., \'ol. XXII, p. o2S. '' Ueber devonische Aiiiiuoiiet'ii, p. 74. 



