1892.] "^1 [Cope. 



is but one neural spine. The chevron bones ore attached at the extremity 

 of the centrum. 



The pubes unite at an acute angle, and have well-developed pectineal 

 process at the middle of their length. The ischia have a prominent 

 tuber. 



The premaxillary and anterior maxillary teeth are simple; the others 

 are tricuspid. 



DiPSosAURUS Hallow. 



The osteology of this genus presents a number of interesting peculiari- 

 ties which constitute difference from Crotaphytus, to which its general 

 appearance suggests affinity. 



Premaxillary bone with elongate superior spine, and posterior emargi- 

 nation of inferior face. Nasals large, distinct, not sliortened in front, 

 since the nostrils open forwards. Frontal narrow, entire, grooved on the 

 middle line below, its posterior region pierced by the pineal foramen 

 which is entirely anterior to the coronal suture (Z). dorsalis). Supraoc- 

 cipital loosely articulated anteriorly, and not distinct from exoccipitals. 

 Prefrontals large, not extending over orbit ; lachrymal smaller, touched by 

 jugal. Postfrontal small, distinct from the large postorbital. The latter 

 articulates extensively with both the jugal and supratemporal. Paroc- 

 cipital small. Parietoquadrate arch well elevated. The vomers together 

 as broad as long, not produced posteriorly, with a median fossa. Palatine 

 flat, with a short maxillary process; pterygoid flat in front, concave on 

 the inner side behind for contact with the long basipterygoid process. 

 Ectopterygoid decurved at its inner extremity. Quadrate with a narrow 

 internal and a wide external couch. Postoptic an open sigmoid, reaching 

 frontal above, with a median expansion with rudiment of posterior limb. 

 Petrosal very short above; subforaminal portion prominent, with a wide 

 inferior groove looking downwards. Epipterygoid leaving pterygoid 

 behind ectopterygoid process, and reaching parietal without contact with 

 petrosal. Presphenoid rudimental; sphenoid and basioccipital united, 

 and with prominent lateral edges. Occipital condyle with exoccipital 

 elements feebly distinguished. 



In the mandible the Meckelian groove is completely curved. The coro- 

 noid has little horizontal extent, and that is principally anteriorly on the 

 external side. The surangular and articular are tused together, and the 

 splenial is small. The deutary extends as far posteriorly as the posterior 

 border of the coronoid. The angle is prominent, flattened so as to be 

 horizontal, and has an internal angle. 



The scapula has a large proscapula directed upwards, and the coracoid 

 has one emargination, which is large. Tlie sternum has a narrow median 

 fontanelle which is not covered by the interclavicle. There are four pairs 

 of ribs articulated to the sternum, and two continue into the approxi- 

 mated xiphoid rods. The ribs reach the sacrum. 



