154 . OPHIDIA. 
along that of the third. A pair of small yellowish spots on the neck; a yellowish 
band across the front part of the snout; lips with a black spot below the eye. Lower 
parts uniform yellowish. 
Length of head 4 lines, of trunk 10 inches, of tail 2 inches 9 lines. 
18. Homalocranium virgatum. (Tab. LII. fig. A.) 
Microdromus virgatus, Ginth. Ann. & Mag. N. H. 1872, ix. p. 17, t. 4. fig. B. 
Homalocranion virgatum, Bocourt, Miss. Se. Mex., Rept. p. 585, t. 36. figg. 4, 4a, (after Giinther). 
? Homalocranion sexfasciatum, Fischer, Abhandl. naturw. Ver. Bremen, vii. p. 225, t. 14. figg. 8- 
10 (1882). 
Hab. Costa Rica, Cartago. 
Nasal generally undivided. Rostral shield just reaching to the upper surface of the 
snout ; anterior frontals scarcely half the size of the posterior, narrow ; vertical five-sided, 
longer than broad ; occipitals as long as the vertical and frontals together, rounded 
behind. Nasal not, or but slightly, in contact with the anteocular. One ante-, two 
postoculars. Seven upper labials, the third and fourth entering the orbit, the hind- 
most the largest. Temporals1+1. The first pair of lower labials not, or but slightly, 
in contact with each other. Anterior chin-shields much larger than the scale-like 
posterior. Ventrals 180 ; subcaudals 71. Upper parts greyish, with a white collar; 
a pair of brown bands edged with black, and two scales broad, run along the back from 
the collar to about the middle of the tail. A similar band along each side of the body, 
and sometimes a narrow blackish line along each side of the abdomen. Lower parts 
uniform white. Upper labials white, with a black spot below the eye and on the 
rostral shield. 
In this species several of the characters which have been used for specific, and even 
generic, distinction, break down. The nasal shield is generally simple, and therefore 
this species ought to be referred to Elapomorphus, which formerly was distinguished 
from Homalocranium by its undivided nasal. But in two of our specimens this shield 
is distinctly divided. Hlapomorphus seems to differ from Homalocranium by the smaller 
number of maxillary teeth. All our specimens of H. virgatum, although varying in the 
extent of the nasal and mental shields, have exactly the same coloration. 
19. Homalocranium bimaculatum. 
Tantilla bimaculata, Cope, Journ. Ac. N. Sc. Phil. viii. p. 148 (1876). 
Homalocranion bimaculatum, Bocourt, Miss. Sc. Mex., Rept. p. 580, t. 36. figg. 6, 6 a-d. 
Hab. Mexico, San Blas (Forrer), Mazatlan (Cope). 
Head very short; eye small, scarcely one-third the length of the snout. Vertical 
shield broad, six-sided, with an obtuse angle in front. Six upper labials; posterior 
nasal in contact with the anteocular; one ante- and one postocular. ‘Temporals 1+1. 
