ART. 12 REVISION OF LIZARDS OF GENUS CTENOSAURA BAILEY 23 



Diagnosis. — This species resembles somewhat Gtenosaura pectinata 

 and brevirostris, but may be distinguished from either of them by the 

 absence of the median dorsal crest over the sacral region. Dorsal 

 crest made up of 65 to 75 short processes and extends only to begin- 

 ning of sacral region. First, second, third, fourth, fifth (and occa- 

 sionally the sixth) caudal whorls of spinous scales separated by three 

 rows of small flat basal scales. 



Distribution. — This species is found on the low coastal plains of 

 western central Mexico. It has been collected in the States of 

 Nayarit and Sinaloa, and it probably occurs also in Jalisco. The 

 type specimens were collected by Bischoff near Mazatlan, in Sinaloa. 

 Other specimens have been collected at Culiacan, Sinaloa, Tepic, San 

 Bias, Maria Madre Island, Tres Marias Island, and Maria Cleofas 

 Island, Nayarit. 



Description. — U.S.N.M. Nos. 7180, adult female stuffed skin, 24630 

 adult male alcoholic specimen. Head normal in length, covered with 

 small hexagonal scales; muzzle slightly decurved. Scales on muzzle 

 larger than other head scales; supraocular small, being separated 

 from each other by three or four rows of scales ; nostrils large, much 

 nearer tip of snout than to orbit, almost tubular, opening obliquely 

 backward; rostral larger than mental; lores flat; 10 to 13 enlarged 

 supralabials; 10 to 12 enlarged sublabials; ear opening as large or 

 almost as large as orbit. Dorsal scales small and smooth, hardly 

 more than half the size of ventrals, being almost granular on neck 

 and gradually increasing in size posteriorly. Dorsal crest made up of 

 65-75 very short processes, which appear as merely elongated com- 

 pressed scales, longer than high, except on interscapular region, where 

 they are as high as long. Three scales on the canthus rostralis, of 

 which the posterior is longer than deep, second deeper than long, and 

 third, adjacent to nares is deeper than long, and divided into a super- 

 ior and an inferior plate; transverse gular fold present; scales on fore 

 and hind legs not spinous. Caudal scales above and laterally in 

 whorls of spinous and flat scales; first seven whorls of spinous scales 

 being separated from each other by three rows of small flat basal 

 scales; next seven whorls by two rows of flat scales and the remainder 

 by one row which itself finally become spinous, giving the distal third 

 of tail a completely spinous appearance. Lower surface of tail covered 

 with transverse series of smaller scales, strongly keeled and pointed 

 posteriorly. Femoral pores 6-6 to 8-8, 



Measurements. — cotypeu.s.N.M. 



No. 7180, female. 



Length of head 45 mm. 



Length of body 165 mm. 



Length of tail 310 mm. 



Total length 520 mm. 



Breadth of head over orbits .^ 23 mm 



