10 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



Proctotretus nigromaculatus. 



Plate IV.— Fig. 2. 



Capite brevi, squamis neque imbricatis nee carinatis, teclo ; auribus margine anteriore 

 tridentato; serie unicd squamarum supralabialium ; squamis temporum magnis, 

 rotundatis, imbricatis ; colli {et prcecipue plicae) eras sis, elevatis ; facie posteriore 

 femorum omnind granulosa ; squamis nonnullis ad latera abdominis gulceqite emargi- 

 natis ; macula transverse oblongd, nigra, supra regionem scapularem. 



Tropidurus (Leiolwmus) nigromaculatus, Weigm. Act. Acad. Cees. Nat. cur. xvii. p. 229. 

 Proctotretus nigromaculatus, Bibr. 1. c. p. 281. 



Habitat, Coquimbo, Chile. 



Description. — Head short, the muzzle rounded, rather obtuse ; scales of the upper part of the head 

 somewhat convex, smooth ; a single line of scales between the labial and orbitar ; ears rather 

 large, the anterior margin having three rather prominent scales, the middle one being the 

 largest. Temporal scales somewhat large, smooth, rounded, and imbricated, those towards the 

 upper part slightly carinated ; those of the sides of the neck thick and elevated, those on the 

 fold being rather acutely prominent ; scales of the back carinated, the carina terminating in an 

 acute point ; a few of the scales at the sides of the abdomen and throat notched ; the remainder 

 of the scales of the under parts rhomboidal. The scales about the axilla and around the base 

 of the shoulder are granular and very small, as are those of the posterior surface of the thighs, 

 on which part there are no imbricated scales as in Tr. Fitzingerii. The tail is round, excepting 

 at the base where it is slightly flattened ; it is moderately long and slender. The anterior 

 extremity placed against the side does not reach to the thigh ; the posterior similarly placed 

 reaches to the shoulder. The colour of this species is yellowish grey above, with a yellowish 

 longitudinal line on each side the back, and two rows of black spots each margined with yellow 

 behind. There is a large and distinct oblong black mark on the region of the scapula, from 

 which circumstance the species takes its name. On the posterior surface of the thighs, towards 

 the upper part, are three or four black dots placed in a line. The under surface is yellowish 

 white with dark grey dots and lines under the chin and throat. 



DIMENSIONS. 



Inches. Lines. 



Length of the head 5 



of the body 1 5 



of the tail 2 8 



Total length .... 4 8 



Length of anterior extremity 8 



of posterior extremity l 2 



This species was first described by Weigmann, and subsequently by M. 

 Bibron, from specimens obtained by Gaudichaud from Coquimbo, at which place 

 the single specimen brought home by Mr. Darwin was also obtained. 



