1834.] 37 [Cope. 



The bones of this specimen are in excellent preservation. They were 

 recovered by Mr. W. F. Cummins from the Peruvian beds of Texas. 



Edaphosaurus microdus, sp. nov. * 



The genus Edaphosaurus Cope, was established on the E. pogontas 

 Cope (Proceed. Amer. Philos. Soc, 1882, p. 448), which is represented by 

 a specimen, which includes only a distorted cranium, with most of the 

 parts preserved. The present species is represented by an individual of 

 which I possess numerous vertebrfE and ribs, and the dentigcrous plates 

 of both jaws. These are part of the dentary splenial in the inferior jaw, 

 and the pterygoid or palatine of the superior. The specimen enables me 

 to determine the characters of part of the vertebral column in the genus 

 Edaphosaurus. 



In the first place the vertebrae possess enormously elongate neural spines, 

 as in Dimetrodon. Next, the centra have a facet on the anterior edge 

 above the middle for the head of the rib, as in a mammal. It is not re- 

 peated on the posterior edge of any of the thirteen centra preserved. 

 Thirdly, the ribs are only compressed proximally. Distally their section 

 is a wide oval. The extremity is truncate and concave. The shaft is hol- 

 low, the walls being thinnest distally. 



Specific characters. The grinding teeth of this species are about as 

 numerous as in the E. pogonias, there being about seven in a transverse row 

 on each plate. They are, however, less closely placed than in the typical 

 species, and have more conic crowns. They do not form a pavement, as 

 they are separated by wider interspaces. 



The centra are rather elongate, and Wie foramen cJiordce dorsalis\s,rSii\\Qr 

 large. No intercentra are preserved, and if present they must have been 

 very small, as the inferior rim of the centrum is not beveled to receive 

 one. The neural spines have transverse processes which commence near 

 the base, and project at intervals from the sides. The inferior ones are 

 oval or subround in section ; those which succeed are more or less com- 

 pressed. The extremities are enlarged fore and aft so as to be claviform 

 in outline, but are compressed except where thickened by lateral tuberosi- 

 ties. These are rarely symmetrical, one being larger and situated higher 

 up, sometimes giving the apex an unsymmetrically bilobate form. Some- 

 times they project at right angles to the terminal expansion. The shaft 

 of the spine has a rather small medullary cavity, and this issues by an 

 open mouth at the summit of the apex without constriction. This pecu- 

 liar arrangement suggests a cartilaginous continuation of the spine which 

 retains the nutritive artery of the medullary cavity. The anterior 

 face of the shaft is grooved from the base for some distance upwards ; the 

 posterior face is plane and then rounded above. 



Measurements. M. 



Diameters of inferior dental patch { anteroposterior 043 



t. transverse 024 



