498 Mr. N. A. Vicors on the Natural Affinities 
Their mode of seizing their prey is conformable to these cha- 
racters: they receive it in full flight into the cavity of their 
mouths, which remain open for that purpose, and where a vis- 
cous exudation within, and a strong reticulated fence of vibrisse 
on the exterior, assist in securing the victim: while, on the 
other hand, the longer-billed families catch their food by their : 
bills. The series of succession in the tribe may be stated* as 
follows, the typical families being placed in the centre : 
Meropide. 
Hirundinide. 
Caprimulgide. 
Todide. 
Halcyonide. 
The family of the Meropide, to which we may first turn our 
attention, as that group of the present tribe, which by the length, 
. Slenderness, and downward curvature of the bill, is most nearly 
connected with the conterminous tribe of Tenuirostres, exhibits 
at first sight a decided discrepancy with the succeeding family 
of Hirundinide, where the bill is short and wide: and if we 
examine only the typical species of each, we must admit that, in 
respect to these particulars, there is a manifest distinction be- 
tween them. Independently, however, of the general characters 
in which both families approach each other, such as the breadth of 
the rictus of the bill, the short and feeble legs, the strength of the 
wing, and the consequent habit of using that member chiefly in 
seeking their support,—we find a gradual approximation take 
place even in their bills: those of some of the extreme species of 
* Or thus, with reference to their typical and aberrant characters : 
Normal group. 
Rostris brevibus, debilioribus, ad ù Hirundinide. 
captandum haud idoneis . . Caprimulgide. 
à LE group. Todide. 
ostri: is, fortioribus, ; 
— skom Halcyonide. 
tandum idoneis......,. s 
Meropide. 
Merops 
