1. CAUSUS. 469 
edge. ostral broader than deep, forming nearly a right angle 
above, its upper portion measuring one half to two thirds its distance’ 
from the frontal; internasals longer than the prefrontals, separated 
from or just touching the loreal; frontal once and a half as long as 
broad, as long as or longer than its distance from the end of the 
snout, longer than the parietals ; two preoculars, two postoculars, 
and one or two suboculars separating the eye from the labials ; 
temporals 2+3 or 4; six upper labials; four lower labials in contact 
with the anterior chin-shields; posterior chin-shields very small or 
indistinct. Scales smooth or faintly keeled, in 19 to 22 rows. 
Ventrals 134-152; anal entire; subcaudals 17-25 pairs. Greyish 
olive above, uniform or with curved or chevron-shaped black cross- 
bars pointing backwards; uniform white beneath. 
Total length 470 millim.); tail 40. 
Sennar, East and Central Africa, Angola. 
a a tg 22; V. 146; Negatana, E. Africa. Dr. J. W. Gregory 
b. Yg. (Sc. 22; V. 143; Mkonumbi, E. Africa. Dr. J. W. Gregory 
23). 
2d. 2 (Se. 22; V. 145; Lamu, E. Africa. ry Fackson, Esq. ) 
C. 18) & yg. (Sc. 21; [P.]. 
V. 146; C. 18). 
aa & Se 22; V. 144; L. Tanganyika. Sir J. Kirk [C.]. | 
(Types of C. jacksontz.) 
J. Yg. (Sc. 19; V. 144; Golungo Alto, Dr. Welwitsch [P.]. 
C. 22). Angola. 
3. Causus defilippii.. * 
Heterodon defilippii, Jan, Arch. Zool. Anat. Phys. ii. 1862, p. 225, 
and Icon. Gén. 11, pl. iv. fig. 8 (1865). 
Causus (Heterophis) rostratus, Giinth. Ann. §& Mag. N. H. (8) xii. 
1863, p. 363, and Proc. Zool. Soc. 1864, p. 115, pl. xv. 
—— rostratus, Mocg. Le Natur. xiv. 1892, p. 35; Bocage, Herp. 
Angola, p. 147 (1895). 
—— defilippii, Mocg. t. ¢. p. 64. 
Snout obtusely pointed, prominent, more or less turned up at the 
end. Rostral large, T-shaped, with obtuse horizontal edge; its 
upper portion forming a right or acute angle behind and quite as 
long as its distance from the frontal; internasals longer than the 
preefrontals and forming a suture with the loreal; frontal once anda 
half to once and two thirds as long as broad, as long as its distance 
from the end of the snout, longer than the parietals; two pre- 
oculars, two postoculars, and one or two suboculars separating the 
eye from the labials; temporals 2+3; six or seven upper labials ; 
three or four lower labials in contact with the very short anterior 
chin-shields ; posterior chin-shields very small or indistinct. Scales 
in 17 rows, dorsals feebly keeled. Ventrals 113-125; anal entire; 
subcaudals 10-18 pairs. Grey or pale brown above, vertebral region 
darker, with a series of large rhomboidal or V-shaped dark brown 
