140 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



Type : It is impossible to determine which one of the specimens is the type. There 

 are numerous representatives of the species, as follows: Nos. 140, 1096 G, 8345 G, 

 8555 G, 1089 G, 2, 132, 133, no number, 1094 G - 8 545 G, 8677 G, 1159 G, 105, no 

 number, 1091 G, 70, 1092 G, 1093 G, 1095 G, 153, and others unnumbered in the 

 American Museum of Natural History; in the U. S. National Museum arc the fol- 

 lowing: Nos. 4458, 4463, 4464, 4514. (Plate 20, fig. 2.) 



Horizon and locality: Linton, Ohio, Coal Measures. 



The most abundant species of the Linton Coal Measures. There are over three 

 dozen specimens preserved in the Newberry collection. The species is a clearly 

 marked one, as a rule, though there is great variation in the size of the body and the 

 form of the vertebrae. Though there are several apparently complete skulls pre- 

 served in the collection, it is impossible to make out the morphology of the ele- 

 ments on account of the amount of crushing to which the skulls have been subjected. 



The head is lancet-shaped, and the muzzle very elongate, slender, and acute at 

 the extremity. The head is in fact 

 a miniature of an ichthyosaur 

 cranium. (Plate 20, fig. 2.) The 

 orbits are large and posterior to 

 the median line. The anterior por- 

 tion of the skull is narrow, poste- 

 riorly truncate, and the mandibular 

 angle is projecting. The posterior 

 portion of the mandible is sculp- 

 tured. Possibly the entire cranium 

 was also, and this has been lost; 

 in fact, this sculpturing is indicated 

 in one or two specimens. The teeth 



. FIG. 30. Restoration of Ptvonius. X I. 



are conical and sharp, longitudi- 

 nally striate, and anisodont. There seemstobe evidence of palatine or pterygoid teeth, 

 though this needs confirmation. The pectoral plates are well preserved, with the 

 interclavicle a narrow oval, with anterior and posterior prolongations. In one speci- 

 men it is sculptured. The clavicles are narrow and slightly sculptured. The abdom- 

 inal scutellae are bristle-like. 



The vertebrae are short, with expanded neural and haemal spines. The expanded 

 condition of the neural spines begins over the thoracic region, where they are low. 

 They become well developed in the posterior dorsal region. The caudal fan-shaped 

 spines are larger. The dilated portions form equilateral triangles which stand on 

 moderately short pedicels. They are weakly ridged, and each ridge is prolonged into 

 a narrow acute tooth beyond the margin, 1 1 of which may be counted on one of the 

 best-preserved spines. The longitudinal striae are terminated near the pedicel by 

 two others which cross obliquely from each side, and, meeting, present the appear- 

 ance of the margin of a cup sculptured in relief, from which the striae arise. Pedicels 

 smooth. The spines are in contact at their angles, thus forming a continuous line. 

 In a typical specimen there are 6 in half an inch, in another 7, and in a third 8. The 

 ribs are well-developed and slender. 



