Cope.] ^^^ [March 18, 



Sauromalus Dumeril. 



The following description of the oi^teology of this genus is based on a 

 skeleton of the S. ater, belonging to the National Museum. 



The premaxillary lias a long spine above and a transverse posterior border 

 below with the anteriorly directed button process. The nasals are well 

 developed and distinct in spite of the large size of the nares. Frontal 

 entire, rather narrow, grooved on the middle line below, and including 

 pineal foramen, which touches the coronal suture. Parietals divided per- 

 haps abnormally in specimen. Supraoccipital loosely attached, but fused 

 with exoccipitals. Prefrontals large, not extending over orbits ; lach- 

 rymals small, in contact with jugal. Postfrontal distinct, small. Apex 

 of postorbital cartilaginous, inferior face in long contact with jugal and 

 supratemporal. Paroccipital not large ; parietoquadrate arch well separated 

 from exoccipital. Postoplic not reaching frontal, superior extremity ex- 

 panded backwards and forwards. Petrosal very short above, prolonged 

 below, inferior groove looking laterally. Fenestra ovale a-nd foramen nervi 

 octavi sunk in deep fossa?. Vomers entirely separated from maxillaries, not 

 produced, but separated by a groove behind. Palatines with a short 

 maxillary process. Palatine foramen moderate ; pterygoids divaricating 

 from each other outwards. Ectopterygoid produced downwards at the 

 posterointernal angle. Pterygoids grooved from basipterygoids backwards 

 on internal side. Quadrate with two conchs, the internal one flat. The 

 epistapedial cartilage is largely ossified. 



Presphenoid a slender rod ; sphenoid and basioccipital confluent. Oc- 

 cipital condyle with exoccipital elements slightly marked above. 



In the mandible Meckel's cartilage is completely enclosed. The splenial 

 is produced but little beyond the splenial foramen. Coronoid extended a 

 little anteriorly at base on external face of ramus, and a little further on 

 the inner side. Dentary extending as far back as coronoid. Articular 

 and surangular distinct. 



The premaxillary and anterior maxillary teeth are simple ; the othe'r 

 maxillaries have two or three denticles anteriorly and one posteriorly. 

 In the dentary bone the teeth (except in front) have two denticles on 

 each edge. 



The hyoid apparatus displays a pair of parallel but separate second 

 ceratobranchials about half as long as the first ceratobranchials. Cerato- 

 liyals slightly expanded proximally, articulated at end of moderately long 

 hypohyals. 



The vertebrfe display a zygosphenal articulation. Five cervicals dis- 

 play free intercentva, and four of them have no ribs. Ribs extending to 

 sacrum. The two sacral centra and diapophj^ses are distinct, but the 

 second diapophysis has a median longitudinal groove. Caudal centra of 

 the distal half of the tail segmented, and possessed for the middle of the 

 length of double diapophyses, between which the fissure passes. Diapo- 

 physes long on basal third of tail. Neural spines low everywhere ; on 

 the caudal vertebrte they stand at the posterior end, and send a keel to 



