406 REPORT OF NATIONAL MUSEUM, 1898. 



coronatum, and six in P. douglassii, exclusive of the iiitercentriim of the 

 atlas, which has no hyi)apophysis. Ribs extend to the sacraui,and are 

 attached to very short diapophyses. The two sacral diapophyses are 

 separated by a wide fissure in the P. coronatum and P. douglassii, but 

 are closely appressed in P. cornutum. On one side of the skeleton of 

 P. douglassii the last lumbar vertebra carries, abnormally, a third sacral 

 diapophysivS which reaches the ilium. Proximal part of caudal verte- 

 brae with long- diapophyses. Caudal centra not segmented. Chevron 

 bones intercentral, not uniting distally. Neural spines everywhere very 

 low, those of the caudal vertebrte single. 



The suprascapula is exceptionally elongate, and the scapula is of 

 moderate length and has a proscapular process. The coracoid has one 

 emargination. The interclavicle is remarkable for the shortness of its 

 posterior limb, which is shorter than the transverse limb in P. cornutum 

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

 very large fontanelle which approaches the jiosterior border. In P. 

 coronatum and P. douglassii three ribs articulate with the sternum, but 

 in P. cornutum two only in my skeleton. The xiphoid rods are widely 

 separated, and carry but one rib. 



The ilium has a short angulus cristm, and the acetabulum is entire. 

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

 approach 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 The pectineal process is obsolete, while the tuber 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 Iguanidse: 

 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. 



Viscera. — The distinction between the large and small intestine is 

 well marked, and there is a large colon, which is set off from the rectum 

 by a strong constriction. The liver is large, and extends farther i)0S- 

 teriorly than in any genus of Iguanidie. The left lobe is larger than 

 in any other genus, extending in most species as for posteriorly as the 

 much narrower right lobe. The posterior border is deeply excavated 

 between them. The mesenteries are of the usual type, except that 

 there is a right hepatoventral in addition to the usual one. It has a 

 position so far to the right side as to be as well termed a hepatolateral. 

 The usual hepatoventral, in consequence of the elongation of the left 

 lobe of the liver, which it follows, extends to or nearly to the trans- 

 verse or cystic mesenteric fold. 



The penis in P. asio is short, and terminates glans-like, in which the 

 rims of opposite sides turn inward toward the obtuse apex on one 

 side. As they turn inward they become separated from the remainder 

 of the glans by a groove, which becomes deep and defines a median lobe 

 between them, which forms the apex of the organ. The grooves do not 

 continue on the side opposite to that on which they originate. The 

 surface of the organ is deeply longitudinally plicate, but at the apex 



