THE STEGANOPODES. 149 



although even here the axillary tracts may be very clearly distinguished by the greater closeness 

 of their plumage from the dorsal tract. The space observed in the dorsal tract in Dysporus is 

 deficient in the Cormorants (Carlo) and Darters (Plotus) ; all other genera have a very distinct 

 spinal space, extending from the shoulder-joint to the commencement of the pelvis. A short, but 

 broad and insulated lateral neck-space is also generally present, but, with this exception, only 

 the inside of the thighs and wings are free from contour-feathers ; the latter, however, contains 

 the large strong parapterum. The number of the powerful remiges is considerable, varying 

 between thirty-six and forty ; their form is very elongate and narrowly pointed, and the first is 

 always the longest. In the tail we usually find twelve, fourteen, or sixteen powerful rectrices. 

 Pelecanus alone has twenty-four small and weak ones. This genus is remarkable for the large 

 size of the oil-gland and the six orifices of each of its halves. Phaeton appears to possess three 

 apertures, but the other genera only one. After these statements there remain only a few 

 peculiarities to be described under the different genera. 



1. Pelecanus. This genus approaches most closely to the Unyuirostres, in the above- 

 mentioned great number and soft texture of its tail-feathers. The covering of contour-feathers is 

 almost uninterrupted, being deficient only on the very narrow inferior space, in the region of the 

 axilla, on the under surface of the arm in the neighbourhood of the wing-membrane, and on the 

 inside of the tibia. I found in the wing thirty-nine true remiges, and about fifteen feathers in 

 each parapterum, of which the lower one especially is very strong. The oil-gland is nearly as 

 large as a hen's egg, and perfectly cordate in form. On the convex upper surface, a little behind 



the middle, a small cordate space is circumscribed by the oil-feathers, and upon this the two 

 sets of six orifices stand close together in two parallel longitudinal rows. The pneumatic 

 texture of the skin already repeatedly mentioned presents the same characteristics as in Dysporus, 

 under which I shall describe it in detail. 



2. Halieus. The species examined by me, H. carlo and africanus, present precisely the 

 same characters of pterylosis as Pelecanus, and have, besides the spaces there mentioned, only 

 one other on each side of the pelvis behind the thighs, which I did not observe in Pelecanus. The 

 aftershaft was entirely wanting. In the wing I found thirty-two remiges in //. carlo, but 

 only twenty-six in //. africanus; in the former the parapterum superius consisted of nine and the 

 p. inferius of six flat principal feathers, and the thumb bore four feathers. Of rectrices I counted 

 fourteen in H. carlo, and in one individual abnormally fifteen ; H. africanus has twelve. I have 

 already spoken (p. 15) of the white spots which the old Cormorants possess in spring on the 

 tibiae and neck, and I repeat that these consist of filoplumes ; but I cannot say whether the larger 

 white spots on the thighs, the feathers of which appear exactly like contour-feathers, are also 

 produced by such filoplumes. 



3. Tachypetes aquila has exactly the pterylosis of Halieus, but has a remarkably sparse 

 arrangement of the feathers, and a distinct spinal space, which reaches from the shoulder-joint to 

 the pelvis. Even a division of the dorsal tract into two halves is indicated by a much stronger 

 structure of its contour-feathers in the interscapulium, but no interval is observed behind these 

 strong feathers. Indeed, as the Frigate-bird differs from the type of the Natatores in many other 

 points, 1 it does so also in its pterylosis, especially in the slight elasticity, the curvature, and par- 



1 One of the most remarkable peculiarities of Tachypetes is the shortness of the tarsi, which 

 is particularly perceptible in the skeleton, and probably occurs in an equal degree in no other bird. 



