EXPLANATION OF THE PLATES. 
PLATE I. 
Emys nigra , Hallow.—Half natural size. 
PLATE II. 
Crolalus ornatus , Hallow. 
a. Side view of head. 
PLATE III. 
Crotalus lecontii, Hallow. 
a. Head from above. 
PLATE IV. 
Figure 1. Crotalus cerastes , Hallow. 
b. Side.—c. Upper view of head, magnified. 
Figure 2. Rldnostoma occipitale, Hallow. 
b. Side.-—c. Upper view of head, magnified. 
Figure 3. Leptophis lateralis , Hallow. 
b. Side.—c. Upper view of head, magnified. 
PLATE V. 
Coronella balteata , Hallow. 
b. Side, and c, upper view of head. 
PLATE VI. 
Figure 1. Dipsosaurus dorsalis , Hallow. 
a. Full view.— b. Portion of under surface.—c. Top of head.— d. Anterior toe and 
claw.—e. Posterior toe and claw.—/. Portion of side.—(The figures 1 c to 1 / 
magnified twice.) 
Figure 2. Sceloporus biseriatus, Hallow, 
a. Full view.— -b. Side of head.—*c. Upper, and d, lower surface of head.—e. Fore 
toe.—/. Hind toe. All magnified twice hut the first. 
PLATE VII. 
Figure 1. Urosaurus graciosus, Hallow. 
a. Full view.— b. Under surface.—c. Top of head.— d. Side of head.— e. Femoral 
pore.—(All magnified three diameters, but the first, which is natural size.) 
