7 



1885-1 [Cope. 



Measurements. M. 



Distance from orbit to free edge of operculum 022 



Length of vertebral column 116 



t^. . c t i ^ (anteroposterior 027 



Diameters of caudal fin < . * nnn 



( vertical 093 



Depth above rib-heads at front of dorsal fin 055 



" below hsenial plates, front of anal fin 044 



The teeth preserved are loose medians, and perhaps laterals, but the 

 reference of the latter is uncertain. The crowns of the former are a little 

 more tban twice as wide as long, and have the extremities a little oblique. 

 The summit is a little flattened, and the sides project a little beyond the 

 base. The surface smooth. Length, M. .010 ; width, .0045. 



The peculiar form of the caudal fin distinguishes this species from most 

 of the known members of the family Pymodontidw. The feeble dorsal 

 and anal fins distinguish it from others, and the discoidal form from still 

 others. 



The structural characters observed in the specimen described have 

 been instructive, especially those of the pectoral fin. These confirm alto- 

 gether my reference of the family of the Pycnodontidce to the Isospondyti 

 as distinguished from the HalecomorpM.* 



The typical and only specimen of this species in the collection is from 

 the southern centre of the Province of Sergipe del Key. It is on a slab of 

 cream-colored calcareous rock which has a coarse slaty cleavage, and 

 probably belongs to the Cretaceous formation, and is of marine origin. 



? BATRACHIA. 

 Stereosternum tumiduii, gen. et sp. nov. 



Char, gen., etc. This genus is known from numerous vertebrae and ribs, 

 sometimes forming consecutive series, but more frequently isolated ; but 

 especially from two slabs, which exhibit the posterior part of a skeleton ; 

 i. e., dorsal vertebrae and ribs, pelvis and posterior limbs, and caudal ver- 

 tebrae. 



The dorsal vertebrae present some of the general characters of the rep- 

 tiles and batrachians of the Permian period. One of these is the existence 

 of a notochordal canal. The small size of the vertebral centrum as com- 

 pared with the arch and its appendages constitutes a resemblance to the 

 batrachian class ; as also do the horizontal position and weak development 

 of the zygapophyses. On the other hand the simple articulation of the 

 ribs resembles that of the Lacertilia in general, though not of any known 

 group of that order ; and has no resemblance to any known reptile of the 

 Carboniferous period. 



The vertebral articular surfaces are both funnel-shaped, the anterior 

 deeply, the posterior shallowly excavated. The dorsal centra are undi- 



* On the classification of the Extinct Fishes of the Lower Types. Proceeds. 

 Araer, Assoc. Adv. Science, 1S7S, p. 292. 



