390 SAURIA. 



is very much developed, and projects over the auricular aperture, 

 being, moreover, provided, upon its projecting margin, with spines or 

 conical plates, the largest of which approximating the occiput. The 

 eyes seem as if situated in the middle of a groove, extending from the 

 snout to the occiput, on account of the projection of the supraciliary 

 ridge and the mastoid region. The lower jaw is generally bordered 

 with a row or two of large plates, which vary in structure and shape, 

 according to the species. The snout is either truncated or acute. The 

 nostrils are conspicuous, and situated near the extremity of the snout, 

 either within the inner margin of the supraciliary ridge, else upon its 

 direct prolongation. The upper surface and sides of the head, not 

 occupied by the spines or tuberculous knobs, are covered with small 

 polygonal plates, varying in size, according to the area over which 

 they extend ; they are exceedingly small in advance and behind the 

 orbits. The surface of these plates is rugose, wrinkled, or keeled, as 

 likewise the surface of the spines themselves. The surface of the eye- 

 lids is covered with minute scales of a granular appearance ; the mar- 

 gin of the eyelid itself is ornamented with a double row of subquad- 

 rangular plates, somewhat larger than the granules just alluded to. 

 The inferior surface of the head, from the chin to the chest, is covered 

 with small scales, characteristic in each species. The neck is generally 

 very short, appearing as if contracted, the result of which contraction 

 would be the presence of several folds of the skin, concealing the auri- 

 cular apertures, placed close to the projection of the temples. 



The scales of the upper surface of the body are very irregular in 

 size and shape ; on the neck, above and below, at the axillae, along 

 the sides of the back, and at the groins, they assume a granular 

 appearance, while along the middle of the back, and on the tail, they 

 appear like thin lamellae, still very irregular, and carinated or sub- 

 carinated. All over the back, sides, tail, and hind limbs, there are 

 large, irregularly pyramidal scales, with an acute point, and a 

 wrinkled or ridged surface. The perif)hery of the abdomen exhibits 

 one, two, or three horizontal series of these pyramidal scales, bent 

 backwards, extending from the fore limbs to the hind ones. The species 

 in which the scales of the back are the largest, is P. coronatum, while 

 that in which the scales are the least developed, is P. modestum, whose 

 external appearance is, in a great measure, destitute of that rough- 

 ness which is generally associated with the idea of these reptiles. 

 The abdominal scales are subquadrangular or rhomboid, either 



