146 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



Without the cranial bones the affinities of this genus can not be determined; 

 while it may be allied to Cocytinus, the vertebras of that form are without peculiar 

 diapophyses. 



Thyrsidium fasciculare Cope. 

 COPE, Geol. Surv. Ohio, n, pt. n, p. 365, pi. xxxi, fig. 2, 1875. 



Type: Specimen No. 8552 G, American Museum of Natural History. 



Horizon and locality: Linton, Ohio, Coal Measures. 



The best preserved example of this species includes 9 vertebrae and the corre- 

 sponding ventral armature. The centra, seen from below, are much contracted in 

 their form, presenting an obtuse median rib, which expands to the articular extrem- 

 ities. In one or two instances the latter are divided by fracture, and the moder- 

 ately concave form of the adjacent surfaces is displayed. The diapophyses are of 

 complex form, but the details are concealed by the prevalent thin layer of coal which 

 invests them. An inferior prominence runs parallel to the centrum; outside of this 

 the process is obscurely trilobate and thickened, not flattened, as in the caudal ver- 

 tebrae of Ptyonins. Several ribs (fig. 8) of moderate thickness appear by the side 

 of the diapophyses. Eleven abdominal ribs in 5 mm. 



The second specimen was originally referred to (Estocephalus rcnicx, as a pos- 

 terior portion of its vertebral column, immediately preceding the caudal series. 



This reference appears to be incorrect, although the resemblance between the 

 corresponding parts in the two genera is no doubt considerable, and the alternative 

 of proposing a new genus and species was not at that time advisable. 



The neural spines are longer than high, and are nearly in contact at their mar- 

 gins; each is marked by about 5 obtuse vertical ribs. A fractured section of the 

 abdominal spines in place displayed at least six layers of them. 



The material on which the above account is based is imperfect. The spec- 

 imen figured by Cope (Geol. Surv. Ohio, vol. n, pt. n, pi. xxxi, fig. 2, 1875) is 

 undoubtedly a portion of the vertebral column of (Estocephalns remex. Nos. 4462 

 and 4480 of the United States National Museum may be representatives of Thyr- 

 sidmm fascicidare, but they are more probably (Estocc Chains remex; if they are the 

 latter this leaves the type as the only known specimen of the species. 



MEASUREMENTS OF TYPE OF THYRSIDIUM FASCICULARE COPE. 



mm. 



Length of portion of vertebral column preserved 7 



Width of ventral armature 1 8 



Length of a vertebra 



Width of same vertebra 4 



