Report of the State Geologist, 93 



fossils;" in other words is a Niagara species. The name of this species 

 has suffered the same obscuration as that of its genus, and has never 

 been admitted to recognition. Barrande observed the close 

 similarity of Warder's figure of (7. goniata to his Odontopleura (1846) 

 or Acidaspis (1852) Verneuili, and has represented on his 

 plate 38 (fig. 3) a cephalon in a similar position to that given 

 by Warder. For the purpose of comparison copies of both are 

 here introduced. It will be observed that the size attained by these 

 closely related animals is very large compared to that usually pre- 

 vailing among members of " Acidaspis." Barrande's species is from a 

 correlative horizon, his etage E^. Professor Hall has described* a 

 species from the Niagara limestone at Bridgeport near Chicago, Acid- 

 aspis Danai, with which the A. Ida, Winchell and Marcy,*!" is a syn- 

 nonym. The figures of this species given by Professor Hall show 

 with sufficient clearness that this form is identical with Ceratocephala 

 goniata. Warder. 



In 1847 Corda described^ the genus Tbapelocera, the first of five 

 species being T. rhabdophora, Corda, which Barrande subsequently 

 showed to be a synonym of his Acidaspis Verneuili, Whatever value 

 this term might have had is therefore lost by its being in all respects 

 synonymous with Ceratocephala. 



Ceratocephala in its restricted sense has this positive value. It 

 embraces such forms as agree with the type G. goniata, in having a 

 large subquadrate cephalon, strong ridges running from the eyes 

 along the outer branch of the facial suture to the anterior extremity 

 of the glabella, and two strong, straight, divergent spines on the axis 

 of the occipital ring. It will include Acidaspis Verneuili and 

 A. tremenda, Barrande, A, vesciculosa, Beyrich, A. hispinosa, McCoy 

 (not Emmrich), A. Barrandii, Fletcher and Salter ; it is of quite 

 restricted range and specific representation. 



The name Acidaspis, proposed by Murchison in 1839, § was founded 

 on the species of A. Brighti, Murchison, the part described being the 

 intra-sutural portion of a cephalon characteriz^ed by the sharp division 

 of the lateral glabellar lobes and the broad occipital ring produced 

 into a single stout median spine. Species of this type of structure 



* Geology of Wisconsin, vol. l, p. 432, 1862. See for illustration Twentieth Beport, N. Y. 

 State Cabinet, pi. 21, figs. 8, 9, 1887 and revised edition, 1870. 



t Memoirs of the Boston Society of Natural History, vol. 1, p. 106, pi. 2, fig. 13, 1865. 



t Prodrom einer Monographie der bohmischen Trilobiten, p. 158. This work, pub- 

 lished over the names of Ignaz Hawle and A. J. C. Corda, has, since the publication by 

 Barrande of a disclaimer by Hawle of any participation in its composition, been gen- 

 erally accredited to Corda alone. 



§ Silurian System, p. 658. 



