1. causus. 465 
Bb ie Causidee, Atractaspidides, Cope, Proc. Ac. Philad. 1864, 
. 231, ° : 
Pp 
Viperida, Strauch, Syn. Viper. p. 18, 1869. 
Abothrophera, Garman, N. Amer. Rept. p. 104 (1883). 
Viperinee, Boulenger, Faun, Ind., Rept. p. 418, 1890. . 
Europe; Asia; Africa. 
Synopsis of the Genera. 
I, Head covered with large symmetrical shields as normal in the 
Colubride ; mandibular teeth well developed ; eye moderate. 
Nostril between two nasals and the internasal; pupil round ; 
scales oblique on the sides ........ 1. Causus, p. 465. 
- Nostril in a single nasal; pupil vertical ; scales not oblique. 
: 2. Azemiops, p. 470. 
II. Some or all of the head-shields broken up into small shields or 
scales; mandibular teeth well developed; eye moderate or 
small, with vertical pupil. 
A. Lateral scales not smaller than dorsals, without serrated keels; 
ventrals rounded; subcaudals in two rows. 
Nasal in contact with the rostral or separated by a naso-rostral 
shield ; postfrontal bone small .... 3. Vipera, p. 471. 
Nasal separated from the rostral by small scales ; a crescentic supra- 
nasal; postfrontal bone very large.. 4. Bitis, p. 492. 
Nasal separated from the rostral by small] scales; no supranasal. 
5. Pseudocerastes, p.501. 
B. Lateral scales smaller than dorsals, disposed obliquely, with 
serrated keels. 
Ventrals angulate laterally ; subcaudals in two rows. 
6, Cerastes, p. 501. 
Ventrals rounded; subcaudals single.. 7. Echis, p. 504. 
C. Lateral scales smaller than dorsals, slightly oblique, the keels 
not serrated ; subcaudals single ; tail prehensile. 
8. Atheris, p. 508. 
III. Head covered with large symmetrical shields; mandibular 
teeth reduced to two or three in the middle of the dentary 
bone ; eye minute, with round pupil ; postfrontal bone absent. 
9. Atractaspis, p. 510. 
1. CAUSUS. 
Causus, Wagler, Syst. Amph. p. 172 (1830); Gray, Cat. Sn. p. 33 
(1849); Dum. §& Bibr. Erp. Gén. vii. p. 1262 (1854); Cope, Proc. 
ace hens 1859, p. 842; Peters, Reise n. Mossamb. iii, p. 143 
Naja, part., Schleg. Phys. Serp. ii. p. 461 (1837). 
Distichurus, Hallow, Journ. Ac. Philad, viii. 1842, p. 337. 
VOL. III. 2H 
