108 



Report of the State Geologist. 



important step further along toward Prolecaiotes. All of the prolecanitoid 

 species are of rare occurrence in the American Devonian ; but a few specimens 

 ^/-n, py /v^^ s °^ Sandberger. syngonum have been found and of 

 Sandberger. C/iemzmgense, Yanuxem, but one has 

 vv\aA(Aa/v-- « been recorded besides the original specimen.* The 

 Figure 82, Suture of sandbar,,, earlier species is the smaller in its adult form, more 



ctras Chemungense, after Wall. l 



Fi K . 8a. suture of sandbergero- primitive in the shape of its whorls and presumably of 



ctrai tuberculosa cnstatum, after - 



sandberger. its suture. The latter species has been found <>nlv 



in association with species characterizing the earlier faunas of the Chemung 

 formation. 



Sandbergerooeras syngonum is from a layer of crinoidal fragments in the 

 lower soft shales of the Portage group at Naples and a single large impression 

 has been found in the bituminous shales constituting the "lower black band " 

 of this group, rocks in which traces of fossils are exceedingly rare. This is 

 also from the town of Naples (Snyder's gully). f 



The species of the upper Devonian which have been referred to Prole- 

 canites, such as Gon. luwdicosta, Sandb., and Gon. Jiecheri, von Buch,J are 

 but very slightly removed from these forms of Satjdbergeroceras. The figures 

 of Gon. lunulicosta given by Frech show very clearly the tendency of the 

 surface ornament to assume the fasciculate character of Sandberger. syngonum, 

 though the development of such bundles is obscure and no nodes or ridges 

 are attained. The broad ventral keel is present in all. Pharck eras, Hyatt, 

 was based upon another similar species, Gon. tridens, Sandb., which Holzapfel 

 and Frech have placed with Prolecanites, but which was separated from that 

 genus on the basis of its divided ventral lobe. Frech's species Pixtlecanites 

 triphyllus is a flat, discoidal shell, wholly Tinlike the typical forms of the 

 genus in this respect, and in its suture it is more like a Sporadoceras than a 

 Prolecanites. 



* This one has been termed Gon. Chemungensis, var. equicostatus, Hall, but there seems to us, after comparison of the 

 original specimens very little ground for the distinction. 



t This specimen was identified by the writer in Bull. 16, U. S Geol. Surv. (p. 51), as Gon. Chemungensis, variety. 



X See Hyatt, op. cit., 1883, p. 335 ; Frech, Geologic der Umgegend von Haiger, Abhandl. zur geol. Specialk. von Preuss. 

 u. d. Thiir. Staat., Bnd. viii, 1887. 



