NATURAL SCIENCES OF PHILADELPHIA. 3 



man's Journal be had proposed the name Halisaurua for a new genus of Mo- 

 sasauroid Reptiles, but as Halosaurus, essentially the same word, had pre- 

 viously been given to a genus of fishes, he wished to substitute for the former 

 the name of Baptosaurus. 



Prof. Marsh also showed a tooth of a rhinoceros from the mioeene of Squan- 

 kuni, N. J., which was the first authentic evidence of this animal east of the 



Mississippi River. It was found in the pits of the Squankum Marl (' pany, 



in the same layer with the remains of the Elotherium Leidyanum Marsh, and 

 was presented to the Yale Museum by Mr. 0. 15. Kiune. The tooth wa 

 last molar of the left under jaw, and indicated an animal about two-thirda 

 the size of the living Indian species. He proposed for it the name Rhino 

 malutinus. 



Jan. 11(7*. 

 The President, Dr. Ruschenberger, in the Chair. 



Twenty-five members present. 



Prop. Leidy directed attention to some fossils, on which he made the fol- 

 lowing remarks : 



1. A specimen consisting of less than the half of a vertebral body, was sub- 

 mitted to my examination by Prof. Hayden, who obtained it last summer 

 during his geological survey. It is from Middle Park, Colorado, and Prof. 

 Hayden thinks was derived from a cretaceous formation. Similar specimens 

 were reported to be not uufrequent, and were known under the appellative of 

 " petrified horse hoofs." The fossil indicates an elongated form of caudal 

 vertebra of some large saurian. Much constricted towards the middle, such 

 specimens would be most liable to break in this position, and the halves from 

 their form might readily be taken, by the inexperienced in such matters, lor 

 what they are called. 



The vertebral body in its entire condition would resemble in form those of 

 Me.galosaurus, but in form and other characters bears a near resemblance to 

 those of Poicilopleuron Bucklandi. This is an extinct reptile from the oolitic 

 formation of Caen, in Normandy, described by Deslouchamps ; and remains 

 apparently of the same animal from the Wealden of Tilgate, England, have 

 also been described by Prof. Owen. 



Poicilopleuron has generally been viewed as a crocodilian reptile with bi- 

 concave vertebra?, but probably pertains to the dinosaurs. The /'. Buck! 

 is estimated by Deslouchamps to have been about 25 feet long. The Colorado 

 fossil indicates a much larger animal, having been more than one-third 

 greater. 



One of the most remarkable characters of the Poicilopleuron is the presence 

 of a large medullary cavity within the bodies of the vertebrae, paralleled 

 among living animals, so far as I know, only in the caudal vertebrae of the ox. 

 The same character is presented by the Colorado fossil. In the former animal 

 the cavi 

 Coloradc 



cavity occupi^o ^uv, iwr^. ...-, *~ 



by a few trabecular The sides of the cavity, converging below, are consti- 

 tuted by a layer two lines thick and as compaet as the walls of the medullary 

 cavity in the limb bones of most ordinary mammals. The upper third of the 

 interior of the body is occupied by the ordinary spongy substance which be- 

 comes more compacted ascending into the interior of the neural arch. The 

 cavernous structure of the Colorado fossil is occupied with crystalline calcite. 

 The estimated length of the vertebral body is six inches or more. The sides 

 are much narrowed towards the middle, and they are concavely depressed just 

 below the sutural conjunction of the neural arch. A narrow groove occupies 



1870.] 



