Report of the State Geologist. 



429 



nasute Dalmanites (D. bicornis) is known to occur in the Niagara fauna 

 at Waldron, Indiana, moreover the characteristic D. limulurus of the 

 Niagara, and D. verrucosus and J), vigilans of the Waldron fauna 

 conform to the Bausmannia type. 



Phacops is represented by P. Logani and P. Hudsonicus (probably 

 the same species). These, together with the P. Trajanus of the Square 

 Lake fauna, are typical Phacopes, i. e. forms in which the glabellar 

 lobes are almost or quite coalesced, the glabella ventricose and the 

 pygidium short. In general this genus divides itself into two groups, 

 in one of which the glabellar furrows are represented by faint linear 

 impressions, and the pleurae of the pygidium are duplicate; in the 

 other the furrows are obsolete and the pygidial pleurae simple. The 

 latter is believed to be limited to Middle-Devonian faunas (P. rana 

 Hamilton, P. latifrons, Eifelian) while the former is widely dissemi- 

 nated as a characteristic Lower-Devonian group, and to this belong all 

 the Lower Helderberg species. Moreover, true Phacops is not known in 

 any earlier American fauna. 



Of Acidaspis we have two species; A. tuberculata is so closely related 

 to the Corniferous A. callicera that it may prove specifically identical 

 with it. The remarkable A. hamata, with long recurved cervical horns, 

 finds its only known analogue, and almost specific identity in the A. 

 monstrosa, Barrande, of the etage G. 



Lichas is represented by forms belonging to the subgenus Conolichas, 

 which finds a later development in the Upper Helderberg. In this 

 group the glabella becomes very tumid and elevated, and in this 

 respect the Lower Helderberg Lichads differ from those of the pre- 

 ceding American faunas (Platynotus, etc.). Conolichas, however, attains 

 a considerable and more typical development in the European Silurian. 



The species of Pro'Ctus (P. protuberans [P. Junius, Square Lake]) are 

 not diagnostic. Their rare occurrence is in sharp contrast to the 

 great development of the genus in the Upper Helderberg, but they 

 conform to the type of structure expressed in the series P. angustifrons 

 of the Schoharie grit, P. clarus of the Corniferous, P. Rowi of the 

 Hamilton, P. marginalis (== P. Rowi) of the Tully. 



Phaethonides makes its earliest appearance in the Lower Helderberg 

 (Ph. cyclurus [Ph. macrobius, Square Lake] ) and is represented in the 

 Schoharie grit, Corniferous and Hamilton faunas. 



Gyphaspis ccelebs (the only species) is allied to both G Christyi of the 

 Niagara and G. minusculus of the Upper Helderberg. 



Lamellibranchiata. The existence of true Pterineas is not yet 

 demonstrated. The abundant Pterineoids are largely Actinopterias 

 and their prolific development stands in sharp contrast to their com- 



