150 PTERYLOGRAPHY. 



ticularly in the distant position of its contour-feathers. I observed down-feathers between these, 

 but, indeed, as also in Pelecanus, only umbellate down-feathers. In the wing I counted 

 thirty-four remiges, of which the ten inserted on the hand are remarkable for their very powerful 

 structure and strong quadrangular shafts. The paraptera consist of from six to eight feathers, 

 and the tail of twelve. 



4. Dysporus. Of this genus I have examined D. bassanus and D. sula, two species well 

 distinguished by the colour of the naked skin of the face, although they are very similar, and 

 also agree perfectly in their pterylosis. The representation of the pterylosis of D. bassanus given 

 in PI. X, figs. 8 and 9, shows all the peculiarities of the family, and appears to indicate a distinct 

 genus only in the short and proportionally broad spinal space in the interscapulium near 

 the axillary tracts. The oil-gland is, however, also remarkable on account of its flat shield-like 

 form, which renders it impossible to distinguish it through the skin as a definitely limited body ; 

 and as the plumage is not deficient at this point, it takes some trouble to discover it. The two 

 orifices which occur on the hinder part of the gland at some distance from its extremity are also 

 very small and difficult of detection, although the closely placed white oil-feathers soon indicate 

 their position. The body of the tail upon which the gland covering the greater part of it lies is 

 remarkably long, and projects considerably behind beyond the gland. On this I found in 

 D. bassanus only twelve, but in D. sula fourteen rectrices, which form a cuneiform tail ; in the 

 wing I counted from twenty-eight to twenty -nine remiges, of which ten are seated on the pinion ; 

 the hypopterum consisted of eighteen feathers. A young specimen of D. bassanus examined by 

 me, although already nearly as large as a Goose, was clothed all over with snow-white down, 

 except on the naked black skin of the face, on which, however, there were also a few minute down- 

 feathers. 



I must dwell a little longer on this genus, in order to describe more particularly the 

 remarkable pneumaticity of the body, which has already been repeatedly referred to, and 

 which extends over a great part of the skin. In the interior of the trunk the air-cells are in 

 their ordinary position, but the large lateral cells are of very considerable size. On the other hand, 

 the hepatic cells are very small, and, as usual, contain no air. Their partition is not firmly 

 attached to the commissure of the liver, but only lies loosely upon it, and, as it were, surrounds it, 

 which I have also found to be the case in the Crane. The smaller or anterior air-cells I only 

 recognised indistinctly, because these air-holders were broken into more divisions than usual. 

 From the latter the air gets under the skin through the axillary cavity, and diffuses itself hence over 

 the entire pectoral and ventral regions, from the furcula to the pubis. These large air-spaces 

 form two cells on each side, but these are connected together and run in a parallel direction 

 side by side. One of them occupies the region of the ribs from the axillary cavity, the other 

 the regions of the sternum and belly, and the latter is contiguous to its fellow of the opposite 

 side, but is separated from it by an aponeurotic partition starting from the crest of the sternum. 

 Consequently, at those places where these air-cavities are situated the skin does not actually rest 

 on the body, but hangs round it and shakes to and fro when the cavities are not full of air. It 

 is, however, particularly remarkable that the skin does not form the immediate outer covering of 

 the above-described air-spaces, but that another thinner and very delicate membrane is stretched 

 between the tips of the contour-feathers inserted in the skin. By this means there is produced 

 between this inner membrane, which forms the true covering of the air-spaces, and the external 

 skin of the body a space of the same height as the portions of the feather-tubes penetrating into 



