NATURAL SCIENCES OF PHILADELPHIA. 135 



Borborocoetes and others, or, more probably, a united or separate pair of 

 free frontal, as in Dactylethra or Rana. There is no trace of the composition 

 of nasals and frontals which occurs in the Gradientia, nor is such an arrange- 

 ment probable, in view of the regular elongate cuneiform outline of this 

 singular piece. A moderately distinct suture crossing the front at the ante- 

 rior third of the interorbital space, which presents a regular convexity for- 

 wards, appears to be the anterior border of the frontal ; the latter can scarcely 

 be an interorbital plate of ethmoid, as it appears to unite behind by suture 

 with the parietals. There are bosses on the prefrontal region indicating 

 prefrontal or " lachrymal " bones similar to those in Sceloporus and other 

 Lacertilian genera. 



What I suppose to be the coronal suture, since it appears to be too regular 

 to be a fracture, crosses the narrowest part of the interorbital space ; it is a 

 zigzag, presenting posteriorly a median angle, and one on each side. The 

 posterior zygomatic arches are strong, and bound a cranial plane, which is 

 broader than long, and exhibits nearly parallel lateral outlines. The probably 

 small " crotaphite foramina " of the temporal fossae appear to have been 

 roofed over by perhaps the strong scales of the cranial integument. The 

 quadratum is convex externally, and is directed obliquely backward to oppo- 

 site the occiput; it is strongly concave in its posterior outline, indicating a 

 large auricular meatus. Whether this was covered by scales or by an exposed 

 tympanic drum, cannot be, determined. The quadratojugale is broad and 

 strong. The postorbital arch is continuous with the quadratum; the breadth 

 of the two equals the frontal width. The angular process of the mandible is 

 but little prolonged beyond the quadratum. The maxillary is toothed at least 

 as far as opposite the malar process. 



The dentition is pleurodont ; the teeth are only visible on the mandible and 

 the outer edge of the upper jaw ; they are there of but one kind, small, closely 

 set, acute-conic, not compressed, hollow, and without any inflections of the 

 enamel. 



The integument of the head was squamous. The scales appear not to have 

 been imbricate, and were perhaps more dense on the posterior regions, where 

 their position is occupied by the white material before spoken of, which has 

 here a somewhat ganoid appearance. They were more elongate on the muz- 

 zle. There appears to have been a distinct superciliary, and a postorbital 

 row, as well as a series on the border of the upper lip. A whorl of elongate 

 scales arranged like the pieces of an arch, surrounded the one on each side 

 which marked the crotaphite foramen. In the specimen these are connected 

 by a suture or line, which is regularly convex posteriorly. The superior pal- 

 pebrae were covered by small separated scales, as are seen among Geccos and 

 Anoles, and were bordered by a larger and continuous series, of about four- 

 teen subquadrate scales. These have evidently bordered the lid, extending 

 transversely across the orbit, and were not sclerotic scales, which are arranged 

 round the pupil as a centre. 



The vertebral column is much injured, especially in the cervical region. 

 The dorsal vertebra? appear to have been short, and probably thirteen in 

 number between the interscapular and sacral regions. They appear to have 

 been constricted medially. Traces of ribs or of transverse processes are not 

 to be found. The impression of a sacral vertebra is distinctly preserved. The 

 caudal vertebrae were perhaps without osseous centra, as no definite im- 

 pressions can be traced, and their place is occupied by the matrix. There 

 are traces of osseous neural arches, perhaps similar to those of Archegosaurus, 

 and apparently disconnected, long, compressed neural spines, and slender 

 pleurapophyses ; the latter were probably united as chevron bones. Of the 

 former, twelve very distinct impressions maybe counted to the sacral region ; 

 the posterior are most slender, the median most elevated, the anterior lower, 

 and of greater longitudinal extent. They are more expanded in the direction 



1865.] 



