154 On a new Snake from Sierra Leone. 



tion in ordinary flight with strokes of the wings, in which, 

 indeed, the kite-like action of the spread of sail always comes 

 jointly into play to a greater or less degree. 



Granted, therefore, that the air-sacs to a certain extent 

 assist respiratory activity, that is, in the case of birds, their 

 main object will still be a mechanical one — the reduction of 

 the specific gravity of the whole animal and the regulation 

 of the specific gravity and the size of its parts, as well as of 

 the position of the centre of gravity. 



XV. — Description of a new Snake from Sierra Leone. 

 By G. A. BOULENGER, F.R.S. 



Aparallactus niger. 



Diameter of eye greater than its distance from the oral 

 margin. Rostral much broader than deep, the portion visible 

 from above one third as long as its distance from the frontal ; 

 internasals slightly broader than long, widely separated from 

 the pra30cular ; a single pra3frontal, forming sutures with the 

 nasal and prteocular ; frontal nearly once and a half as long 

 as broad, as long as its distance from the end of the snout, 

 much shorter than the parietals ; nasal semidivided, in con- 

 tact with the pra^ocular ; two postoculars ; a single temporal ; 

 seven upper labials, third and fourtii entering the eye, fifth 

 and sixth in contact with the parietal ; first lower labial in 

 contact with its fellow behind the sympliysial ; anterior chin- 

 shields longer than tiie posterior, in contact with four lower 

 labials. Scales in 15 rows. Ventrals 164; anal entire; 

 subcaudals 60. Uniform black above ; ventrals white, edged 

 with black ; subcaudals black in the middle and on the 

 posterior and outer borders. 



Total length 335 millim. ; tail 80. 



A single male specimen iu a small collection made by 

 Mr. W. G. Clements in Sierra Leone. 



The same collection contained a specimen (head and neck 

 only) of Naia Ouentheri, Blgr., the habitat of which was 

 still unknown. 



