No. l8.] / TRIASSIC FISHES OF CONNECTICUT. 67 



maximum depth of the trunk, and contained four times in the 

 total length of the fish. Fins as in vS\ firitus. Scales smooth 

 and serrated, those of the middle of the flank in part twice as 

 deep as broad. The dorsal ridge-scale immediately in advance 

 of the dorsal fin has its posterior border obtuse, and not pro- 

 duced, and the corresponding ridge-scale in front of the anal 

 fin is notched behind. Ribs more strongly developed than in any 

 other species of the genus. 



This, the commonest form occurring within the Connecticut 

 Valley area, is as a rule easily determinable, its most conspicuous 

 features being the abrupt elevation of the dorsal outline im- 

 mediately behind the head, and the spiny appearance of the 

 back occasioned by its being set along the middle with long, 

 thickened, and distally pointed or clavate ridge-scales. The 

 ribs also are more strongly developed than in other species, their 

 curved outlines being sometimes traceable even when covered 

 with scales. Owing to the frequency with which this species 

 has been illustrated, and the impossibility of mistaking it among 

 collections of Triassic fishes, it has not been deemed essential to 

 include a figure of it in the present Report. 



5\ tenuiceps outnumbers all other species in the Connecticut 

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

 Turner's Falls and at Sunderland, Massachusetts, it is especially 

 common, probably more than half of the individuals derived from 

 the latter locality pertaining to this form. 



Semionotus micropterus (Newberry). 

 (Plate IV.) 



1888. Ischypterus micropterus J. S. Newberry, Trans. 



N. Y. Acad. Sci., vi, p. 127 (name only). 

 1888. Ischypterus micropterus J. S. Newberry, Monogr. 



U. S. Geol. Surv., xiv, p. 31, pi. 4, figs. 1, 2; 



pi. 12, fig. 2. 

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



March 18, and Pop. Science, May, 1899, p. 98. 

 1903. Semionotus micropterus G. F. Eaton, Amer. Journ. 



Sci., [4] xv, p. 263, pi. 5, figs. 6-8, 11, 13. 

 1905. Semionotus micropterus C. R. Eastman, Ann. Rept. 



N. J. Geol. Surv. for 1904, p. 87, pi. 2, figs. 6-8. 



