THE STATE GEOLOGIST. 87 



is notched behind. Ribs more strongly developed than in any 

 •other species. 



It is usually possible to determine this form with great facility, 

 even in the case of fragmentary remains, none of the other species 

 having the back so much elevated immediately behind the head, and 

 set along the middle with such long, thickened, distally pointed 

 or clavate scales. The ribs are also more conspicuous than in 

 most other species, their curved outlines showing sometimes even 

 when covered with scales. Owing to> the frequency with which 

 this species has been illustrated, and impossibility of mistaking it 

 amongst collections, it has not been considered necessary to 

 figure it in the present report. 



S. tcnuiceps outnumbers all other species in the Connecticut 

 Valley Trias, and is tolerably abundant also in New Jersey. At 

 Turners Falls and at Sunderland, Mass., it is especially common, 

 probably more than one-half of the individuals derived from the 

 latter locality pertaining to this form. 



Semionotus micropterus (Newberry). 



(Plate II, Figs. 6-8, n, 13.) 



1888. Ischyptcrus micropterus, J. S. Newberry, Trans. N. Y. Acad Sci., vol. 



vi., p. 127 (name only). 

 1888. Ischypterus micropterus, J. S. Newberry, Monogr. U. S. Geol. Surv., 



vol. xiv., p. 31, pi. iv., Figs. I, 2; pi. xii., Fig. 2. 

 1893. Ischypterus newberryi, S. W. Loper, Pop. Sci. News, p. 

 1903. Semionotus micropterus, G. F. Eaton, Amer. Journ. Sci. [4], vol. xv., 



p. 263, pi. v., Figs. 6-8. 



D. 8;C. 15; A. 8. 



A regularly fusiform species attaining a total length to the 

 base of caudal fin of about 20 cm., the maximum depth occurring 

 in the pectoral region and not exceeding 8 cm. The dorsal and 

 ventral contours are more strongly convex than in >S\ fultus, but 

 the relative position and size of the fins are about the same in 

 the two species. Dorsal, anal and pectoral fin-fulcra relatively 

 shorter than in S. fultus. Apparently three dorsal fin-fulcra 

 originate on the dorsal line over the interneurals. The fifth 

 dorsal fulcrum has its origin on the anterior margin of the an- 



