238 PALiEONTOLOGY OF NEW-YORK. 



298. 2. CALYMENE SENARIA. 



Pl. LXIV. Figs. 3 a - n. 



Calymene Blumenbachii. Green, Monograph, 1832, pag. 28 (Cast no. 1). 



— callicijihala. Id. lb. pag. 30 (Cast no. 2). 



— selenecephala. Id. lb. pag. 31 (Cast no. 3). 



— senaria. Conrad, Ann. Geol. Rep. New-York, 1841, p. 41). 



— — Emmons, Geol. Report, 1842, pag. 300, fig. 2. 



Compare Calymene Blumenbachii, Brongniart, Dalman, Wahlenberg, Hisinger, Murchison, &c. 

 See also Calymene Blmnenbachii of the higher strata of New- York, in this Report. 



Buckler semicircular or sublunate, regularly rounded in front, or slightly projecting in 

 front of the glabella, with a distinct thoracic ring at the base ; posterior angles subacute 

 or rounded ; glal>ella separated from the cheeks by a deep broad groove, wider behind or 

 often of nearly equal width throughout, with three tubercles or lobes on each side, the 

 anterior one often obscure ; cheeks triangular ; eyes truncato-conical, situated a little out- 

 ward from the inner edge of the cheek ; facial suture terminating nearly in front of the 

 eye ; thorax with thirteen segments, those of the lateral lobes with a deep groove extending 

 from the base more than half way to the extremities ; caudal shield small, with seven 

 segments in the middle lobe and five in each lateral one, the latter with an impressed line 

 or shallow groove the whole length. 



This species is very abundant in the dark compact portions of the Trenton limestone, 

 though perfect individuals are comparatively rare. 



A comparison of specimens from this rock in New- York and Ohio, with those from 

 Gothland in Sweden, shows no essential difference. Tlie only difference in the Niagara 

 specimens is a rougher granulation of the surface, and a slightly greater width of the front 

 of the glabella, which latter character is variable from different causes. The large specimens 

 fronj the Schoharie grit present a slight difference in ihe direction of the facial suture, as 

 well as some other characters which may prove essential in the designation of the species. 



On comparison with a well preserved specimen of the Calymene blumenbachii from Dudley 

 in England, the most obvious difference consists in the slight but conspicuous tuberculation 

 of the segments of the middle lobe of the thorax, at their extremities. The articulations of 

 the lateral lobes of the caudal shield show a strong impressed line towards their extremities, 

 but not towards the base, as in well preserved Trenton specimens. The glabella of the 

 Dudley specimen is broader in front than tliat of the Trenton species, and its surface is 

 more coarsely granulated. In other respects, the two resemble each other. 



Fig. 3 a. A large specimen from the Trenton limestone, with the buckler abruptly curved downward 



in front. This specimen is of unusually largo size. 

 Fig. 3 i. A small specimen from the same rock. 3 c. Lateral view of the same. 

 Fig. Z d. A. small specimen from the Hudson-river group, showing no essential difference of cliaracter. 

 Fig. 3 e,f, g. Three views of a contracted specimen from the Bhie limestone of Ohio. 



This is the C. callicepkala of Green ; but I am unable to perceive any essential dif- 



