84 OPHIBOLUS. 



from 0. Boylil in having the light intervals in the form of spots in 

 the centres of dark scales, instead of covering the whole space. The 

 lateral blotches are alternate with those of the back, not continuous 

 and opposite. The blotches are more numerous. 

 Sonora,Mex. 219.65.23. 36. 5|. Col. J. D. Graham. 



" 215. 55. 23. 26. 4. " 



B. Dorsal rows 21. 



3. Opilibolus SayJ, B. & G. — Black, each scale above with a large 

 circular or yellow spot in the centre. Sometimes only transverse lines of 

 these spots across the back. 



Syn. Herpetodryas getulus, Schl. Ess. Phys. Serp. Part, descr. II, 1837, 198. 

 CoroneUa Sayi, Holbr. (non Schl.) N. Amer. Herp. Ill, 1842, 99. PI. xxii. 

 Coluber Sayi, Dekay, New York Fauna, Kept. 1842, 41. 

 King Snake. 



As already remarked, we consider this as the true type of the 

 genus, and shall accordingly reproduce some of the generic features 

 in more detail. 



Body, as in most of the other species, very tense and rigid, with 

 difficulty capable of being extended after immersion in alcohol. 

 Vertical plate triangular, wider than long ; outer edge slightly con- 

 vex, an angle being faintly indicated at the junction of the super- 

 ciliaries and occipitals ; shorter than the occipitals, which are short, 

 longer than broad. Postfrontals large, broad; anterior smaller. 

 Rostral small, not projecting, slightly wedged between prefrontals. 

 Eye very small, orbit about as high as the labial below it ; centre 

 of the eye a little anterior to the middle of the commissure, over the 

 junction of the 3d and 4th labials. One anteorbital, vertically 

 quadrate ; loral half its height, square. Upper labials 7, increasing 

 to the penultimate. Lower labials 9 ; 4th and 5th largest. 



Scales nearly as high as long, hexagonal, truncated at each end. 

 Dorsal rows 21, exterior rather larger, and diminishing almost im- 

 perceptibly to the back, although all the scales in a single oblique 

 row are of very nearly the same shape and size. 



The scales on the back and sides are lustrous black, each one with 

 a central elliptical or subcircular spot of ivory-white, which on the 

 sides occupy nearly the whole of the scale, but are smaller towards 

 the back, where they involve one-half to one-third of the length. 

 Beneath yellowish white, with broad distinct blotches of black, more 



