104 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



The interest in the present specimen is heightened by the light it throws on the 

 characters for the separation of the Amphibia and Reptilia. The wide separation 

 of the pterygoids by the parasphenoid is an amphibian character of undoubted value. 

 The reduction of the parasphenoid in this specimen is noteworthy. 



MEASUREMENTS OF THE SKULL OF ERPETOSAURUS TABULATUS COPE. 

 (No. 8607 G, American Museum of Natural History.) 



mm. mm. 



Length of skull in median line .. . 45 Width of pterygoid. . 5 



Estimated posterior width of skull. . . 50 Length of ectopterygoid. . 17 



Estimated width of parasphenoid. . t> Posterior width of mandible 12 



Erpetosaurus minutus Moodie. 

 MOODIE, Proc. U. S. Nat. Mus., 37, pp. 21-23, pi. 8, fig. i, 1909. 



Type: Specimen No. 4545, U. S. National Museum. 



Horizon and locality: Cannelton slates, Pennsylvania (Upper Freeport). 

 (Plate 20 D.) 



The specimen on which the species is based is composed of the greater portion 

 of a small skull preserved in the hard shale from Cannelton, Pennsylvania, and was 

 collected by Mr. R. D. Lacoe, of Pittston, Pennsylvania. The characters of the 

 specimen had not previously been determined, since the museum label and number 

 had partially obscured the snout of the skull. The skull is very small, but has the 

 form assumed by other members of the genus. The specimen may belong to a young 

 individual, but even though it does, it is, nevertheless, quite distinct from the other 

 species of Erpetosaurus. At first sight the specimen looks like a broken scute of 

 some larger form. Close inspection, however, revealed the two impressions repre- 

 senting the orbits, and a Zeiss binocular revealed the characters. The large size 

 and anterior position of the orbits, the character of the sculpturing, the presence of 

 the posterior table of the skull, as in Erpetosaurus (Tuditanus) tabitlatus Cope, are 

 the characters on which a specific diagnosis is possible. The specific characters 

 which distinguish this form from E. tabulatus Cope, its nearest ally, are the slight 

 development of the posterior table, the more delicate form of the sculpturing, the 

 more posterior position of the orbits, and the varying shape assumed by the parie- 

 tals in the two species. Any one of these characters would be valid as a specific 

 character. 



The pineal eye is indistinct, but is observed to lie in the broken tract in the 

 median line of the skull, in the middle of the portion posterior to the orbits. The 

 interorbital space is equal to the width of the orbit. The orbits themselves are 

 slightly oval and not round, as in the case of E. tabulatus Cope. 



The skull elements are sculptured with radiating grooves and ridges, and on the 

 postparietals and tabulare the grooves take the form of pits in a row, which undoubt- 

 edly represent the occipital cross-commissure of the lateral-line system first observed 

 in a microsaurian by Andrews (8) in the skull of Ceraterpeton galvani Huxley. The 

 supraorbital canal is represented by a slight elongate depression observable over 

 each orbit and extending, in one case, for about 5 mm. The presence of the circular 

 arrangement of the lateral-line canals in the jugal region is suggested by a depres- 

 sion on the posterior edge of the squamosal. 



