CROCODILIANS, LIZARDS, AND SNAKES. 541 



infraorbital fossa. Limbs well developed. Clavicle dilated, loop-shaped 

 proximally : interclaviele T-shaped. No abdominal ribs. Head covered 

 with symmetrical shields, without dermal ossificatious. Body granular 

 or tubercular above, plated inferiorly. No movable eyelids. 



The hemipenis is bifurcate in Xantusia, and is shortened, as in many 

 Geckonidiie, appropriately to the fragile tail. There is a welt on each 

 side of the sulcus spermaticus, which follows a short spiral direction. 

 Opposite to the sulcus are two short thick welts, which have the direc- 

 tion of parts of consecutive threads of a screw. All of the welts are 

 deeply cross folded. 



The position of this family in the system has been discussed by M. 

 Bocourt' and myself.- I associated the genera Xantusia Baird, Lepido- 

 phi/ma Dumeril, and Cricosaura Peters, and stated that I was not able to 

 distinguish them from the family Lacertidce. M. Bocourt places these 

 genera in the family " Trachydermi," which also includes Heloderma 

 Wiegmann. This family is divided by M. Bocourt into two subfamilies, 

 the Glyphodonti for Heloderma^ and the Aglyphodonti for the th.ee 

 genera named, together with Xenosaiirus Peters. Previously to this-' I 

 had examined and compared the osteology of the Heloderma and XenO- 

 saurus. On account of the differences in the form of the mesosternum 

 and in some other points, I regard Xenosaurus as the type of a peculiar 

 family to be placed with the Helodermidce in the tribe Diploglossa. 

 Xantitsia, Lepidophyma, and Cricosaura are, on the other hand, not 

 Diploglossa, but are Leptoglossa. They are allied to the Lacertidte, 

 and especially to the Asiatic Ophiops, which is, like them, without eye- 

 lids. The character of the tongue is, like that of the Ecpleopidie, uni- 

 formly squamous, and has no resemblance to that of the Diploglossa. 

 The characters of the scapular arch are those of tlie Leptoglossa. The 

 clavicle is loop-shaped proximally and the mesosternum is cruciform in 

 Lepidophyma and Xantusia. I have not been able to examine Crico- 

 saura as to these points. In my paper first mentioned I stated that 

 these genera have distinct parietal bones. I think that they should, 

 on this account, be distinguished from the Lacertidie, where they are 

 coossified. 



The genera of Xantusiidiii are the iollowing : 



I. One frontal and one frontonasal plates. 



Superciliary scales, none ; pupil round Lepidophyma Dumeril. 



Superciliaries present ; pupil verti cal Xantusia Baird. 



II. One frontal, two frontonasals. Pupil erect. 



An iuteroccipital plate; frontoparietals in contact; superciliaries. 



Zablej)8i,s Cope. 

 No iuteroccipital; frontoparietals widely separate; superciliaries. 



^ Cricosaura Peters. 



III. Twofrontals; one frontonasal; pupil erect; no iuteroccipital; frontoparietals 



not widely separate ; superciliaries Amahopsia Cope. 



' Mission Scientifique de Mexique, Herpetolqgy, 1878, p. 303. 



-Proceedings of the Academy of Natural Scieuces, Philadelphia, 1864, iJ. 229. 



'Idem., 1866, p. 3l'2. 



