84 BULLETIN 17 5, UNITED STATES NATIONAL MUSEUM 



The dentition is as follows: Mandibular teeth 18 to 22, decreasing 

 slightly in size posteriorly ; maxillary teeth 16 to 18, decreasing slightly 

 in size posteriorly ; palatines 9 to 11 , slightly smaller than mandibular 

 and maxillary teeth, pterygoids 11 to 14, slightly smaller than pala- 

 tines, and decreasing in size posteriorly. 



The dorsum bears a series of large median spots, which are generally 

 distinctly saddle-shaped anteriorly, and become less or not at all so 

 posteriorly. These vary from 34 to 63 (average 44.8) on the body and 

 from 10 to 18 (average 11.9) on the tail, are each 3 to 7 scales in length 

 and 8 to 12 scales in width, and are separated by light interspaces of 

 2 to 7 scales long in the vertebral line. In color the dorsal spots are 

 either black or reddish brown on the anterior part of the body, reddish 

 brown in the middle of the body, and black on the posterior third 

 of the dorsum and on the tail. The ground color is a yellowish white, 

 except in the interspaces between the dorsal spots, where it is notice- 

 ably orange. Each side bears three series of smaller dark spots, 

 which follow the dorsal series in color, and alternate with one another 

 and with the dorsal series. In the midregion of the body, where the 

 spots are reddish, frequently each scale mcluded in the spots of both 

 the lateral and the median series bears a small black spot centrally or 

 at the posterior tip. The belly is white and bears a series of small 

 dark spots on either side, and occasionally additional black spots 

 scattered irregularly between these lateral series posteriorly and on 

 the under side of the tail, where they frequently fuse to form a single 

 dark median streak. The top of the head is pale or reddish brown, 

 and the throat is yellowish white (fig. 42). 



Variation. — Although the number of specimens studied is much 

 smaller than is desirable in a study of geographic variation, some 

 variations appear to exist that may be of some significance, although 

 they cannot be accepted as conclusive. In the accompanying graphs, 

 the regions represented by specimens have been numbered 1, 2, 3, 

 etc., along the abscissas, A key to the regions is as follows: 



Region L California: Jim Grey, San Bernardino County; Fort Reading. 



2. Northern part of Lower California: Onyx Mine, San Pedro, and 



Alamo. 



3. Central part of Lower California: San Ignacio, Ballenas Bay. 



4. Southern part of Lower California, except the extreme tip: Miraflores, 



La Paz, San Bartolo, Santa Anita, Aqua Caliente, Trinidad, San 

 Antonio. 



5. Extreme southern tip of Lower California: Cape San Lucas, San Jos6 



del Cabo. 



6. Cerros Island, Lower California. 



7. Margarita Island, and Magdalena Island, Lower California. 



The island specimens have been graphed as separate units, since it 

 is evident that they cannot be introduced properly at any given point 

 in a continuous geographic series, and they will not be included in the 

 following discussion, except when explicitly mentioned. 



