34 A REVISION OF THE COTYI.OSAURIA OF NORTH AMERICA 



Genus PARIOTICHUS Cope. 



Pariotichus Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, pp. 508 and 529. (Also Pal. Bull. 29.) 

 EctocynoJon Cope, Proc. Am. Phil. Soc., vol. xx, 1882, p. 450. (Also Pal. Bull. 35.) 

 Pariotichus Cope, Proc. Am. Phil. Soc., vol. xxxiv, 1896, p. 443. 



Type: A skull which has lost the outer layer of bone and the occipital region. 

 No. 4328 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Homotype. A second skull in good condition. No. 4760 Am. Mus. Nat. Hist. 

 Cope Coll. From Texas. 



Original description: "The temporal fossae were covered by a roof continuous 

 with the postorbital region; the zygomatic arch extends low down, producing a 

 resemblance to certain tortoises. The orbits are small and lateral, and the muzzle 

 is short, with terminal nares. Their exact character can not be ascertained. The 

 teeth are rooted, and have compressed obtuse crowns, with cutting edge; they di- 

 minish in length posteriorly and do not display any elongate canine. The cranial 

 bones do not exhibit any sculpture." 



In 1883 "Proceedings American Philosophical Society" (p. 631) this last state- 

 ment was corrected: "The surface of the cranium has been mostly weathered away 

 in the type of Pariotichus^ P. brachyops, and I suspect that it is really sculptured 

 and not smooth, as I originally stated." 



In 1896 an analytical table of the genera of the Pariotichidee was given. In 

 this table the genus Ectocynodon is united with Pariotichus and many of the species 

 of Captorhinus are regarded as belonging in the genus. 



"I. External nostrils lateral. 



a. Palatal and splenial teeth with compressed crowns. 



Teeth equal, acute Isoiectts Cope. 



Teeth increasing gradually in length anteriorly Captorhinus Cope. 



Teeth enlarged on the middle of the maxillary and anterior part of the incisive 



series Pariotichus Cope. 



aa. Palatal and splenial teeth obtuse, forming a grinding pavement. 



Median maxillary and anterior incisor teeth enlarged Panlylus Copt. 



II. External nostrils inferior. 



Mouth posterior in position, mandible short, and with a few acute teeth . . . Hypopnous Cope. 

 "It is probable that Helodectes Cope pertains to this family." 



Revised description: See description of Pariotichus brachyops. 



Pariotichus brachyops Cope. 

 Cope, Proc. Am. Phil. Soc., vol. xvii, 1878, p. 508; Proc. Am. Phil. Soc., vol. xxxiv, 1896, p. 445. 



Type: An imperfect skull. No. 4328. Am. Mus. Nat. Hist. Cope Coll. 

 From Texas. 



Homotype: A skull. No. 4760 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: "The interorbital width is twice the diameter of an orbit, 

 and is nearly flat. The cheeks behind the orbits are swollen; the canthus rostralis 

 is obtuse, broadly rounded, and somewhat depressed; the nostrils were not large. 

 The orbits are subround, and measured half of the length of the muzzle measured 

 axially above. The mandibular rami are not deep. The longest teeth are below 

 and in front of the anterior border of the orbit; posterior to this point they diminish 

 rapidly and are reduced to a very small size. The crowns of the greater number of 

 the teeth are short and much compressed, and the enamel is coarsely longitudinally 

 grooved. An anterior mandibular tooth has a subconic crown. 



"Measurements. M 



"Width of the skull at the parietal region 0.020 



Length of skull from parietal region 022 



Interorbital width 010 



Four teeth in 004 



Lcngthof root and crown of a tooth 002" 



