298 COLUBRID#. 
111. DIROSEMA. 
Maxillary short, with 10 to 16 teeth, the anterior and posterior 
of which are the shortest; mandibular teeth small, decreasing in 
length posteriorly. Head distinct from neck; eye small, with 
vertically elliptic pupil; preocular absent, loreal and prefrontal 
entering the eye. Body moderately elongate, cylindrical; scales 
without pits, smooth or feebly keeled, in 15 or 17 rows; ventrals 
rounded. ‘Tail short; subcaudals in two rows. 
Central America. 
Connects T'ropidodipsas with Geophis. 
Synopsis of the Species. 
I. Scales in 17 rows. 
Nostril between two nasals; fifth upper 
labial largest; scales smooth,..+.... 1. bicolor, p. 298. 
Nostril between two nasals ; sixth upper 
labial largest; scales faintly keeled .. 2. omiltemanum, p. 299. 
Nasal undivided; sixth upper labial 
largest; scales keeled..::........: 3. psephotum, p. 299. 
SE Scales in 15 POWs... 2 dss se bMs ede 4. brachycephalum, 
[p. 299. 
1. Dirosema,bicolor, (Prare XIV. fig. 2.) = 
Geophis bicolor, Giinth. Ann. § Mag. N. H. (4) i. 1868, p. 416, 
and Biol. C-Am., Rept. p. 91 (1898). 
Rhabdosoma guttulatum, Cope, Proc. Amer. Philos, Soc. xxii. 1885, 
p. 385. 
Snout broad, rounded. Rostral a little broader than deep, visible 
from above ; internasals much broader than long, two fifths to one 
half the length of the prefrontals ; frontal as long as broad or a 
little broader than long, as long as its distance from the end of the 
snout; nostril between two rather large nasals; loreal twice as long 
as deep; two postoculars (rarely one); temporals 1+2 or 1+1+2; 
six upper labials, third and fourth entering the eye, fifth largest and 
usually in contact with the parietal; two pairs of chin-shields, 
anterior longest and in contact with three or four lower labials. 
Seales smooth, in 17 rows. Ventrals 151-168; anal entire; sub- 
caudals 38-50. Black above, with a more or less distinct lateral 
series of whitish dots; the scales of the two or three outer series 
white in the centre ; upper lip white; lower parts white, uniform 
or spotted with black. 
Total length 425 millim. ; tail 95. 
Mexico. 
a-d. 3 (V.159,151;C.47, City of Mexico. Mr. Doorman [C.]. 
50) & 2 (V. 167, 168; (Types.) 
C. 88, 41). 
e-f,g. & (V. 149; C. 46) LaCumbre de los Arra- Dy. A. C. Buller 
& 9 (V. 163,161; C. 42, strados, Jalisco, 8500 {C.]. 
46). ft. 
