1800.] ^^^ [Cope. 



Leptodira mystacina, C'ojye. 



Scales in nineteen longitudinal series. Body very slightly compressed, 

 head distinct, an elongate oval. Superior labials seven, the second in 

 contact with the upper and lower preoculars, third and fourth with orbit, 

 and fifth with occipital excluding the temporal. Fourth, fifth, and 

 sixth higher than long ; temporals 1-1-2. Oculars 2-2, inferior small in 

 both sets. Internasals long as wide, prefrontals longer than wide. 

 Frontal longer than wide, with parallel sides, considerably in contact 

 with superior ocular. Occipitals oval, scarcely emarginate behind. 

 Postgeneials longer than than pregeneials. Gastrosteges 187, anal 1-1, 

 urosteges 70. 



The ground color is a dirty white, and is uniform below. Above it, 

 marked by very broad cross-bands, which extend to the gastrosteges and 

 are twice as wide as the intervals of ground. There are thirteen to the 

 vent ; on the posterior half of the body they divide on the vertebral 

 line, and alternate ; one is thus continuous with two of an opposite side, 

 leaving the ground in lateral squares. Head above, including occipitals, 

 a lighter speckled brown above, leaving a white collar. A black band 

 from eye to angle of mouth, and a second from below the eye to mouth, 

 parallel to the above, encloses with it a light band ; a black band from 

 eye to nostril ; lips in front black spotted. Total length 16.25 inches ; of 

 mouth 7 lines ; of tail 4.25. 



Habitat. The western region of Mexico, near the Isthmus of Tehuan- 

 tepec, two specimens (251-261) sent to the Smithsonian Institution by 

 Francis Sumichrast. This serpent approaches very near the L. pacifica 

 Cope in details, but differs totally in coloration. The structural difier- 

 euces are the following : 



Ij. fnystacina. L. pacifica. 



Head elongate oval ; Head short wide. 



Preocular reaching frontal ; Pi-eocular not reaching. 

 Prefrontals longer than wide ; P. f. wider than long. 

 Fifth labial to occipital ; Fifth labial not to occipital. 



Trimokphodon, Cope. 

 Proceed. Acad. Nat. Sci., Phila., 1861, 297. 



This peculiar genus, hitherto not found outside of the Mexican, Cen- 

 tral-American and Sonoran districts, is well illustrated by the collections 

 received by the Smithsonian Institution. Two species have been hith- 

 erto known, and I now add three others, as follows : 



I. Scales in 21-3 Bows. 

 Seven (six) superior labials ; three loreals ; head black in front with 

 a white T shaped mark ; back with uniform black rhombs. 



T. TAU. 



Eight superior labials ; head broad, short ; three loreals ; head dark- 

 brown, with light cross-bar on muzzle and between eyes, and V on oc- 

 ciput ; body with broad brown annuli ; tail one-fifth the total. 



T. UPSILON. 

 A. P. S. — VOL. XI — T 



