OF THE SPINAL TRACT. 23 



commencement of the portion of the tract behind the gap is cleft, as I have found to be the case 

 in several species of the genus Bucco, as circumscribed by Linne and Latham. 



7. Continuous and strong, narrow on the neck, but widened from the shoulder-blades, and 

 at the same time not divided longitudinally. I have seen this form of the spinal tract in 

 PJiasianus, Gallas, Numida, Perdix (P. cinerea and P. coturnix), Crypturus (Plate VII, fig. 12), 

 and Musophaga paul'ma (Plate VI, fig. 9). 



8. Like the preceding form, but the broader portion is cleft by a longitudinal space from the 

 shoulders onwards. Examples of this tract are furnished by Tetrao uroyallm, Perdix javanica, 

 and Hemipodius. In the Pigeons the same structure occurs, but in them the feathers at the 

 commencement of the widened part between the shoulders are much stronger, and represent a 

 bilobed saddle (Plate VII, fig. 2). When the modification just indicated is destitute of the 

 longitudinal space it passes into the eleventh form. 



9. Continuous and strong throughout, elliptico-lanceolate on the back, and enclosing, in 

 this widened part, a long and likewise lanceolate space. This form, which readily passes into the 

 fifth, when the saddle is abbreviated, or into the tenth when the space reaches to the end of the 

 tract, occurs in several families of birds, namely, among the Macrochires, in the genera Trochilus 

 (Plate III, fig. 19), Cypseltts (Plate III, fig. 17), and Hemiprocne NOB. ; in the Cuculine genera 

 Galbula (Plate IV, fig. 8), Scythrops, Nyctornis NOB. (Nydibius VIEILL., Plate IV, fig. 4), Phce- 

 nicoplianes, Centropus (Plate IV, fig. 14), Crotophaga and Cuculus (Plate IV, fig. 12); also in 

 Upupa (Plate VI, fig. 4) belonging to the family Lipoglossa ; in some Fulicaria, such as Fulica, 

 Rallus (Plate VIII, fig. 6), and Gallinula ; and, lastly, in Dicholophm, which genus I associate 

 with the Alectorides. 



10. Continuous and narrow, furcately divided between the shoulder-blades, but not uniting 

 again afterwards, giving origin to a right and a left dorsal tract, both of which are continued to 

 the tail. I have found this very singular form only in Rhamphastos (Plate V, fig. 1 3) and 

 Pteroylossus. Sometimes the tract is weakened exactly at the point of division, where it then 

 appears to be interrupted. 



11. Interrupted at the ends of the shoulder-blades in such a manner that the anterior free 

 part is separated partly by a true and partly by a false gap of varying size from the posterior 

 covered part. The anterior part is very strong, gradually becomes broader, and furcate ; the 

 posterior part is weaker, generally narrow, and neither partially dilated nor cleft. A spinal 

 tract of this kind is possessed by most of the rapacious birds, and among the diurnal forms by 

 the genera Aetos, NOB. (including Aqnila and Buteo of authors), Circus, Milvus, Elanus, Pernis 

 (Plate II, fig. 4), Astur, Polyborus, Morpknus, and many others, all of which I unite in the single 

 genus Falco, excluding from it, however, the genera Rhynchodon NOB. (Fulco AUCTT. sensu stricto, 

 Plate II, fig. 6), and Pandion. It likewise occurs in Gypogeranus, Gypaetos (Plate II, fig. 2), 

 Vultur, Neophron, and Catkartes, although in the last three the commencement of the cervical 

 portion is wanting. In the nocturnal raptores two bands formed of several series of feathers 

 unite the fork with the posterior part of the tract (Plate II, figs. 9, 10), and precisely the same 

 thing occurs in Gypaetos and Pernis, except that in these each band consists only of one series of 

 feathers, which is rarely met with in the Owls. A similar spinal tract is also presented by many 

 species of the genus Psittacus (Plate V, fig. 17), and likewise in Coracias (Plate IV, fig. 6), 

 Opistkocomus (Plate VI, fig. 13), Eurypyga (Plate VIII, fig. 15), Diomedea (Plate X, fig. 4), and 

 T/talassodroma, 



