Cope.] •^^O [March 18, 



gination. The interclavlcle is remarkable for the shortness of its poste- 

 rior limb, which is shorter tlian the transverse limb in P. cornutum and 

 P. douglassii, and equal to it in P. coronatmn. The sternum has a very 

 large fontanelle which approaches the posterior border. In P. coronatum 

 and P. douglassii three ribs articulate with the sternum, but in P. cornu- 

 tum two only in my skeleton. The xiphoid rods are widely separated, 

 and carry but one rib. 



The ilium has a short angulas cristce, and the acetabulum is entire. 

 The pubis and ischium are slender and transverse in position, and ap- 

 proach nearly at their symphyses, which are connected by a short, narrow 

 cartilage. The pectineal process is obsolete, while the tuber ischii is a 

 prominent angle. 



Two peculiarities especially distinguish this genus among Iguaniilje : 

 first, the connection of the epipterygoid with the petrosal ; and, second, 

 the absence of symphysis of the chevron bones. The characters of the 

 sternum are an extreme of what is seen in Sceloporus. 



Gerkhonotus Wiegm. 



A skeleton of the G. multicarinalus from the U. S. National Museum, 

 furnishes the material for an osteology of this genus. 



The premaxillary has a well-developed spine and a truncate palatal 

 border. Its alveolar border is short, and it forms but a small part of the 

 inferior nareal border. Nasal bones not short in front, rather nar- 

 rowed by the maxillary and prefontals on each side. Frontal narrow, 

 single, partly enclosing olfactory lobes of the brain below, but the in- 

 curved lateral walls not touching. Parietal with small pineal foramen 

 far behind coronal suture. Supraoccipital loosely articulated, and sepa- 

 rated by suture from exoccipitals. Prefrontal not tuberiferous, produced 

 posterior to middle of supraorbital border. Postlrontal cresceutic equally 

 united with frontal and parietal. Postorbital splint-shaped, with very 

 slight contact with the jugal, and long contact with the suprateraporal. 

 Jugal slender, reaching anteriorly the small lachrymal. Paroccipital nar- 

 rowly exposed posteriorly, well produced upwards on the distinct parieto- 

 quadrate arch. Quadrate with one deeply excavated concli, which is 

 external. Vomers in close apposition in front, separated by a fissure poste- 

 riorly ; the anterior portion excavated medially. Palatines descending 

 from the plane of the vomers, the vomerine and maxillary processes 

 about equal ; main plate rather narrow. Palatine foramen large. 

 Pterygoid contracting gradually into posterior slender portion ; basiptery- 

 goid well developed. Presphenoid wanting. Sphenoid and basioccipital 

 separated by suture ; descending tuberosities of the latter strong, com- 

 pressed. Epipterygoid originating below opposite basipterygoid ; above 

 resting on anterior process of petrosal, and touching parietal just behind 

 an obtuse descending angle of the decurved border of the same. Sub- 

 foraminal portion of petrosal shorter than supraforaminal portion, en- 



