12 THE HISTOKY OF THE PELYCOSAURIA, WITH 



teriorly, and are separated by a notched diastema from the large canine. The succeeding 

 teeth are of medium proportion. There is no surface sculpture of the cranial bones." 

 The vertebras and intercentra, the greatly elevated neural spines in the lumbar and 

 sacral regions are described, the humerus with the entepicondylar foramen and the ectepi- 

 condylar groove. The ilium, ischium and femur. In regard to the relationship of 

 Clepsydrops, Cope makes the following remarks : " Of the general affinities of this genus 

 it is only necessary now to state, that my reference of it to the Rhynchocephalia is con- 

 firmed. It differs from the recent species of the order in the absence of quadratojugal 

 arch and the remarkably developed ischia. On this account I refer to Clepsydrops and 

 its allies as a distinct suborder under the name of Pelycosaubia." 



The new genus Dimetrodon is larger than Clepsydrops. The dentition is similar to 

 that genus. The roots of the teeth are long and are contained in deep alveoli. Between 

 the premaxillary and maxillary is a deep emargination of the border of the jaws. There 

 are but two incisor teeth, of which the anterior is much larger than the second. The 

 anterior two teeth of the maxillary bone are larger than the following ones, the anterior 

 exceeding even the first incisor. The other maxillary teeth are smaller and subequal. 

 The orbit is lateral, and has a prominent and convex suj)erciliary border. The zygo- 

 matic arch is so curved upwards as to complete the orbit behind by the intervention of a 

 postorbital or postfrontal bone, which separates the malar [jugal] and squamosal bones 

 from mutual contact. In front of this bone a portion of "the frontal forms the super- 

 ciliary border, and in front of this, the prefrontal sends a wide process behind the 

 lachrymal to the orbit. This bone resembles a nasal bone in form, and extends forward, 

 and is decurved at the extremity. The width of the descending or malar process of the 

 postfrontal is such as to partially separate the orbit from the zygomatic fossa. The super- 

 ciliary surface is swollen, and is interrupted by a transverse groove on the orbital part of 

 the prefrontal. There is a vertical open groove on the malar process of the postfrontal. 

 Some pelvic bones are referred here. They include both the ilia, ischia and pubes in 

 one mass, forming a compressed boat-shaped body, with a prominent inferior keel. They 

 probably belong to Eryops. 



Dimetrodon is said to be allied to Deuterosaurus Eichw. and Eurosaurus Fisch., 

 as defined by Meyer. " Deuterosaurus has much more elevated nostrils, more numerous 

 incisor teeth, and wants the extensive diastema in front of the superior canine. 

 I/ycosaurus Owen, from the South African Trias, resembles it much more nearly, but 

 does not present the greatly enlarged anterior incisor teeth of Dimetrodon." 



The new genera and species, Epicordylus erythroliticus Cope and Metarmosaurus 

 fossatus Cope, which are based on vertebra?, are considered closely related to Dimetrodon. 

 The new genera, Embolophorus, with one species, E. fritillus, and Theropleura, with 



