Cope.] 9) 2 [March 3, 
spect. It, however, further differs in the relatively more compressed or 
oval centrum, and much greater size. From ZZ. minor the present reptile 
differs in the opisthocoelian vertebra, the known caudals of the former 
having plane articular surfaces, and in the much larger size. It is not 
possible to compare similar parts of this species and the Ornithotarsus 
immanis, Cope, hut the larger size and much lower stratigraphic horizon 
of the latter renders their identity very doubtful. 
Should the genus Thespestus of Leidy turn out to be well eatablished, 
the present species will enter it. Iam not, however, entirely satisfied that 
the difference in the form of the articular faces of the caudal vertebrae is 
such as indicates generic difference. It was on this ground that I referred 
this form to Iudrosaurus (in Synopsis Extinct Batr. Rept. N. Amer., 
p. 98), and not from misapprehension of Leidy’s definition of it, as the 
latter supposes (Proceed. Aca. Nat. Sci., 1870, p. 67). 
The rather slight material above described is fortunately so character- 
istic as to enable us to establish satisfactorily the existence of another 
monster of the remarkable group of the Dinosauria; beings, whose ap- 
pearance and structure have rivalled the strangest creations of the 
imagination, and shown again what every other page of the book of 
nature teaches, that reality is stranger than fiction. 
On Two extinct forms of Physostomi of the Neotropical Region. 
By E. D. Cops, A. M. 
(Read before the American Philosophical Soetety, March 3, 1871.) 
Fam. ELOPID JE. 
PRYMNETES, Cope. 
Dorsal fin above the anal with short basis and very elongate rays ; the 
posterior ray free and longer than the others. Ventrals posterior. 
Vertebre with deep lateral grooves, disproportionally numerous in the 
abdominal region, viz.: Abd. 49, caudal 18. Tail deeply bifurcated, its 
exterior or supporting rays, like those of the dorsal, ventral and pectoral, 
very stout and obliquely segmented. Head short, mouth (in the specimen) 
inferior; teeth simple, small. Scales with many concentric grooves and 
a few radii on the proximal portion. No lateral line discoverable. 
The pertinence of this genus to the Elopide is indicated in various 
ways.. The general form is that of Hlops and Megalops, and the normal 
and supernumerary ribs are quite as in the former. The interneural 
spines extending from the head to the dorsal fin, are quite like those of 
the same genus. It differs from both in the posterior position of dorsal 
fin, and relatively numerous abdominal vertebrae. From lops it differs 
especially in the long posterior lash-like ray of the dorsal, and the deeply 
grooved vertebre. 
PRYMNETES LONGIVENTER, Cope, sp. nov. 
Established on a very fine and nearly perfect specimen, preserved on a 
