1896.] -^^^ [Smith. 



ceras, Gli/pJiioceras, Gastrioceras, Paralegoceras, Nomhmoeeras, Pericy- 

 clus, Dimorpltoceras, with numerous subgenera. They comprise many 

 rough-shelled species, and on this account they are thought by Stein- 

 mann* to have given rise to the trachyostracan Ceratitidm and Tropi- 

 tidcE of the Trias. In this opinion also concurs Dr. K. A. von Zittel.f 

 as far as the TropiUdce. are concerned, for these, he thinks, liave been 

 developed out of Gastrioc-eras and Pericyclas. 



The Prolecanitidce of the Carboniferous comprise the genera Prole- 

 canites, Pronorites. Agathieeras; all of which live on into the Permian 

 and branch out during that period into a number of genera and sub- 

 genera. Some of these genera live on into the Trias, and branch out 

 during that i^eriod into numerous f\imilies, whose Jurassic and Creta- 

 ceous descendants made up the bulk of the cephalopod faunas. 



Besides the Goniatitidcn and the Prolecanitida of the Carboniferous, 

 the Ammonoidea are represented already in the Coal Measures of 

 America by the fiimilies Arcestida, in Popmioceras parkeriX Heilprin, of 

 the StraAvn division, Lower Coal Measures of Texas. 



In the European Coal Measures the TropiUdce are represented by 

 Thalassoceras looneyi Phillips. Thalassoceras Avas described by Gem- 

 mellarog to include certain species of the Carboniferous and Permian, 

 and referred to the TropiUdce ; thi^ genus, along with ParacelUtes Gem- 

 mellaro, Gastrioceras, and some Permian forms referred to GlypMoce- 

 ras, are said by Mojsisovics|| to he the Paleozoic representatives of the 

 TropiUdce. 



Family GoniaUtidce von Buch (Zittel). 

 Subfiimily GlyphioceraHdce Hyatt. 



This group includes a series of forms that range from the Upper De- 

 vonian into the Permian. The older members have the siphonal lobe 

 undivided, thus showing their relationship to the older ProlecaniUdcB. 

 The form may be compressed and discoidal as in Brancocerus of the De- 

 vonian and Carboniferous ; or broadly rounded and involute, with 

 semilunular cross-section, as in most species of Glypldoceras ; or evo- 

 lute, with wide umbilicus, trapezoidal cross-section, and umbilical I'ibs, 

 as in most species of Gastvioeeras. The sutures are simple, consisting 

 of a siphonal lobe, which may or may not be divided by a secondary 

 siphonal saddle, and one or two pairs of lateral lobes, which are some- 

 what pointed, also usually a pair of short lobes on the umbilical shoul- 

 ders. The internal lobes consist of a long and rather pointed antisi- 



* Elemente der Palaeontulooie, 1890, p. 393. 



t Qrundziige der Palxonlologk, 1895, ]>. 405. 



X The writer, in Journ. GeoL, Vol. ii, No. 2, p. 194, following Karpinsky in Ammoneen d. 

 Artinsk-Stufe, p. 92, referred the Popanoceras parkeri beds to the Artiusk stage, but Prof. 

 W. F. Cummins, of the Geological Survey of Texas, has pointed out to the writer the 

 true horizon of this species. 



§ Oio)~nale Sci. Nat. Econom., Vol. xix, 1888, p. 67. 



II Das Gebirge um Hallsladt, Bd. ii, p. 10 



