856 REPORT OF NATIONAL MUSEUM, 1898. 



longitudiual bands behind frontal rciiion ; all the markings beconiiug 

 obsolete in a general brown color with maturity. 



The head is rather long and narrow. The prefrontals are each longer 

 than wide; the frontal is not narrowed; the parietals are truncate 

 behind. The suture between the loreal and prefrontal is oblique, run- 

 ning i)osteriorly down ward, so that its superior border is only half as long 

 as the inferior. The preocular does not reach the frontal. There are, 

 as in other Mexican species of the genus, but two postoculars. The eye 

 is over the fourth and fifth labial. None of the labials behind the fifth 

 is elevated, but the sixth is elongate so as to border the ends of the 

 three long temporal scuta. The inferior of these covers the seventh and 

 part of the eighth labials and supports above it two others like it, all 

 being directed downward and forward. The superior incloses a little 

 scale with the superior postocular. Inferior labials, eleven; geneials 

 well developed, the posterior smaller and separated by scales. 



In a young specimen 450 mm. in length, where the color markings 

 have not become obsolete, there are seventy-six dorsal spots, of which 

 fifty-one are between the nape and the vent. These spots are trans- 

 versely quadrate, covering eleven scales transversely and two and a 

 half scales anteroposteriorly. They are dark brown with light edges 

 and paler centers. The interspaces are less than two scales long. The 

 lateral spots are opposite the intervals and are in one row; they are 

 subround or suboval. There are two brown stripes on the nape which, 

 instead of uniting at both ends, as is the case in the G.Jiavirufus, are 

 separate posteriorly and diverge anteriorly, extending to above the pos- 

 terior part of the orbits. Between them another band occupies the mid- 

 dle line, but is more or less broken. A broad brown band convex for- 

 ward between the fronts of the orbits. A brown spot behind orbit. 

 Below, immaculate. Gastrosteges, two hundred and eighty-two; anal 

 double; urosteges, one hundred and nine. 



Measurements. — Total length, 1.090 mm.; tail, 235 mm. 



Slight variations sometimes occur in the (7. mutabilis. One specimen 

 has thirty-five rows of scales; another has but tw^o rows of temporals 

 on one side; another has nine superior labials on one side. 



Of the Coluber mutahilis I have before me four specimens from Vera 

 Paz, from Mr. Hague; one from the plateau of Costa Eica, from Mr. Zele- 

 don, and one from the central or elevated part of the State of Oaxaca, 

 from Mr. Sumichrast. I have examined a seventh specimen in the col- 

 lection of Prof. Alfredo Duges, who took it in the State of Guanajuato. 

 Dr. Duges informs me that it has been also found near Leon, so that 

 there is no doubt that it belongs to the plateau of Mexi(;o as well as to 

 that of Guatemala. According to the same author it occurs also in San 

 Luis Potosi and in Guerrero. 



Dr. Boulenger, in the Catalogue of Snakes in the British Museum, 

 has confused this species with the triaspis Cope. The difierences 

 between the species are enumerated in the analytical table on page 828. 



