A DESCRIPTION OF THE GENUS DIMETRODON, COPE. 



17 



The characters of Dimetrodon cruciger Cope, already given in American Naturalist, 

 December, 1878, p. 830, are noted again. 



A new genus Helodectes is established. It has the molar teeth in two series. Two 

 species are named H. paridens and II isacii. 



In the American Naturalist of February, 1881, Prof. Cope 11 gave a list of the Verte- 

 brates of the Permian Formation of the United States. 



The following Reptilia are catalogued : 



Theromorpha Cope. 

 Pelycosauria Cope. 



Diplocaulidce. 



Diplocaulus salamandroides Cope, Eastern Illinois. 

 Clepsydropsidce. 



Parioticlius brachiops Cope, Texas. 

 Ectocynodon ordinatus Cope, Texas. 

 Archmobelus vellicatus Cope, Eastern Illinois. 

 Clepsydrops collettii Cope, Eastern Illinois. 

 vinslomi Cope, Eastern Illinois. 

 " pedunculatus Cope, Eastern Illinois. 

 " natalis Cope, Texas. 

 Dimetrodon incisivus Cope, Texas. 



" rectiformis Cope, Texas. 



" biradicatits Cope, Texas. 



" gigas Cope, Texas. 



" cruciger Cope, Texas. 



Theropleura retroversa Cope, Texas. 



Theropleura uniformis Cope, Texas. 

 " triangulata Cope, Texas. 



obtusidens Cope, Texas. 

 Metarmosaurus fossatus Cope, Texas. 

 Embolophorus fritillus Cope, Texas. 

 Lysorophus tricarinatus Cope, Eastern Illinois. 

 Bolosauridce. 



Bolosaurus striatus Cope, Texas. 

 Diadectidce. 

 Diadectes sideropelicus Cope, Texas. 



" phaseolinus Cope, Texas. 

 Empedocles alatus, Cope, Texas. 



" latibuccatus Cope, Texas. 



" molaris Cope, Texas. 



Helodectes paridens Cope, Texas. 



" isacii Cope, Texas. 



The next paper of Cope 12 is " On Some New Bratrachia and Reptilia from the Per- 

 mian Beds of Texas." A new species of Dimetrodon is described under the name of D. 

 semiradicatus ; based on premaxillary and maxillary bones. There are three teeth on each 

 premaxillary ; in the maxillary 17 or 18. The first premaxillary and third maxillary 

 are of nearly equal size and are much larger than the others, the second premaxillary 

 only approaching them. Besides, the clavicles of Dimetrodon cruciger are discussed and 

 compared with the corresponding elements of the Stegocephali. 



In November, 1884, Prof. Cope 13 published his fifth contribution to the knowledge of 

 the Permian Vertebrates. A new species of Clepsydrops, C. leptocephalus, is described. 

 " This species is represented by almost the entire skeleton, the principal deficiency being 

 that of the scapular arch and the anterior limbs, with the phalanges of the posterior 

 feet." 



The bones of the skull are mostly preserved. The quadrate bones are rather short, 

 and articulate above by squamosal suture with the squamosals, which overlap them pos- 



a. p. s. — vol. xx. c. 



