PICARLE. 85 



graphically Hirundo does not differ from the rest, but rather harmonises completely with 

 Dictum (see Plate III, fig. 14), in that the rows of single contour-feathers uniting the saddle with 

 the rump-band are either entirely deficient (H. rustica, urbicd], or indicated only by two rows of 

 very sparse contour-feathers (H. rupesfris). The dilatation of the pectoral part of the inferior 

 tract is somewhat divergent at the end. The number of remiges is eighteen, of which nine are 

 on the hand, and of these the first is the longest ; the first six secondaries are remarkable on 

 account of their broad, emarginate extremities. Tail forked, but the outer feathers are remarkably 

 elongated only in //. urbica. 



CHAPTER III. 

 PICIFORM BIRDS (Picarice). 



THE group of Piciform Birds is the most various of all, both as regards the general structure 

 of the body and the pterylosis, and in regard to the latter I know of no single character which 

 is peculiar to it. It usually agrees with the Passerinse in the want of down-feathers upon most 

 of the spaces and all the tracts ; but in Alcedo both parts are downy, as in Cinclus. The presence 

 of the aftershaft is here not even a character of the subordinate families, but merely a generic 

 character. I have found it in Cypselus, Trocliilus, Caprimulgus, Coracias, Prionites, Leptosomus, 

 Prodotes, Trogon, Micropogon, Pogonias, Jynx, Pirns (in which, however, it is very small), 

 Psittacus (in which it is of considerable size, not exceeded by that of the GaUinaceae), Musophaga, 

 and Colius, whilst it is decidedly wanting in all the other genera of this family examined by me. 

 A similar difference is exhibited in the feathering of the apex of the oil-gland, which is so 

 constantly deficient in the Passerinse. I have found it in most of the genera, although sometimes 

 very imperfect, but I decidedly have not seen it in Caprimvlffits, Coracias, Prionites, Merops, Galbula, 

 any of the CucitlincE, Capita, and Monastes. The total absence of this gland in many Parrots 

 (see p. 39) considerably increases this want of uniformity in the character of the group. 



When primary differences of structure are to be found in such small parts and organs, we 

 shall not be surprised to find still greater variations in the arrangement of the tracts, and to see 

 in them scarcely anything more than generic characters. It is therefore impossible to give a 

 pterylographic description of the families, and I have only been struck by the general sparsely 

 feathered structure of the tracts, which becomes more considerable and strongly marked in 

 proportion as the genera consist of constant inhabitants of the tropical zones. It is also 

 impossible to cite differences of numbers in particular definitely feathered parts as group : pecu- 

 liarities, as these are not less multifarious than the other structures ; nevertheless, I may remark 

 that the Humming-birds possess only sixteen remiges, the smallest number of all, whilst twenty- 

 seven or twenty-eight occur in Buceros, and that this number is exceeded in no genus of Piciform 

 Birds, and, indeed, is rarely attained, from twenty to twenty-three being the usual number. The 



