CROCODILIANS, LIZARDS, AND SNAKES. 191 



are inferior i)rocesses of tlie cervical centra in some forms, tlie hypapo- 

 physes of Owen. These have been confused with the- intercentra by 

 Bouleuger, and have been renamed catapophyses by Baur.' 



The lirst dorsal vertebra is that one which is first connected with the 

 sternum by a luemapophysis. In genera with a well-developed sternum 

 the number of vertebrae anterior to the first dorsal is eight, except in 

 the yara7ius niloHcus (Cuvier) and V. (/risens, where it is nine. In the 

 extinct Dolichosauria of the Cretaceous period the cervical vertebrae 

 are stated by Owen to number seventeen. 



The number of ribs attached to the sternum diminishes with the 

 reduction of the limbs, from the normal of four on each side to one, and 

 total disconnection. A common hsemapophysis or "xiphoid rod" suc- 

 ceeds these on each side, which gives attachment to two separate hoema- 

 pophyses for ribs. The common lijiemapophysis is a segmentation of 

 the anterior part of the fifth ha^mapophysis, and it is not distinct 

 in some genera, as, Sanromalus. In Heloderma the fifth haemapo- 

 physis has no sternal segment or connection, and the sixth is want- 

 ing. In Varanus the fourth, fifth, and sixth are wanting. In genera 

 with the two appendicular hiemaijophyses they are closely appressed 

 on the middle line in the majority of the genera, but in genera of 

 depressed form they are separated, often widely. They are sei)arated 

 in Steuodactylus guttatus, in rhyviaturus, Crotaphytus, and Sceloporus. 

 They are more widely separated in Bipsosaurus, and most widely in 

 Sauromalus and Phrynosoma. Cervical libs are present in varying 

 numbers, and the posterior ones are generally (piite elongate. In cer- 

 tain genera and families the ribs posterior to those attached to the 

 sternum have their h;emapoi)hyses fused on the middle line below, thus 

 constituting a series of abdominal ribs. In the Jguauid genus Scartis- 

 ens there are two such ribs. In the Auolidw there are four and five 

 pairs; in the Polychroine Iguanidse there are seven to ten. In the 

 Chama^leonida^ and Geckonida* there are several pairs. The ribs of 

 Ijcpidosterniim are remarkable for the presence of a capitular process 

 which has no distinct capitular articulation. 



Scapular arch. — The clavicle is present in all the families except the 

 Chamu'leonida", and in certain genera witli degerierate fore limbs. In 

 such genera it is the last portion of the scapular arch to remain, and it 

 is the only element present in FeyUnia (Anelytropsidte). It is always 

 osseous. The form of its proximal extremity varies in the different 

 families. It is simple in the Nyctisaura, Uroplatoidea, Acrodonta, 

 Iguania, Diploglossa, and Thecaglossa, and expanded and generally 

 perforate in the other superfamilies where present, except in some 

 degenerate genera where it is simple (see Plate II, fig. 2). In Tracliy- 

 mnruH and Cophias its proximal end is dilated, but not perforate. The 

 scapula varies in form from elongate to short and wide. It presents a 



'Proceedings, U. S. National Museum, XVII, 1891, p. 351. 



