142 PTERYLOGRAPHY. 



this two tract-bands originate a rather broad one on the back, and a narrow one at the angle of 

 the throat. These are separated by the rather broad lateral neck-spaces. The former remains 

 simple as far as the scapulas, and then divides into a fork, the tolerably strong branches of which 

 terminate before reaching the extremities of the shoulder-blades. At this point the dorsal tract 

 is usually interrupted by a true gap, but in Lestris parasitica this is either entirely wanting or 

 very imperfect. The following posterior part is at first weakened in proportion as the gap 

 appears more distinctly; it then commences with two parallel rows of feathers between the 

 arms of the fork, and these become widened on the outside posteriorly, and at the same time grow 

 somewhat stronger, only coalescing at the caudal pit to form a short, strong stem, which runs to 

 the oil-gland, and apparently terminates at it. From this posterior part the lumbar tracts are 

 generally quite separate ; in Lestris catarrhactes alone, in which they stand much more obliquely, 

 they touch the stem of the uropygial band. The inferior tract -which, as we have seen, issues 

 simple from the plumage of the throat, remains undivided as far as the middle of the neck, when 

 it separates into two divergent limbs, and continuing in this condition over the middle of the 

 furcula, passes on to the pectoral surface. Here it immediately forms an outer branch, sometimes 

 quite free, sometimes free only in its posterior half; this is somewhat stronger than the main 

 band, and terminates rather far back, at the margin of the mmculus pectoralis major. The 

 somewhat narrower and weaker main band at first turns inwards, and approaches nearest to its 

 fellow at the middle of the sternal crest ; from this point the two bands diverge, form a curve on 

 the belly, where they become rather broader and stronger, and terminate close to the anus. The 

 rest of the plumage presents no special peculiarities. On the humerus, which is remarkable for 

 its great length, there is beneath a strong hypopterum, which also appears upon the breast, but 

 is not actually connected with the outer branch of the inferior tract. This part of the wing is in 

 other respects a mere space ; but the upper surface has a continuous plumage, separated from the 

 strong axillary tracts by a small space which is particularly insignificant behind. On the 

 contour-feathers I observed a weak, fluffy aftershaft. The large, broad oil-gland, which is 

 strongly truncated behind, bears a dense circlet of oil-feathers, and has frequently, perhaps 

 always, several orifices in each half. 



1. Sterna (PI. IX, figs. 11 and 12). In this genus, in consequence of the slender and 

 elegant form of the body, the tracts are very narrow, and perfectly Scolopacine ; but in other 

 respects correspond with the general description above given. Of the species examined, namely, 

 8. caspia, leucopareia, Mr undo, arctica, TEMM., fissipes and minuta, the first has thirty-three 

 remiges, the following three twenty-nine, and the last two only twenty-six, of which the first is 

 always the longest, and ten are seated on the pinion. The tail contains twelve feathers, and is 

 generally furcate, although the two outermost feathers are not always the longest, but sometimes 

 two others; for example, in S. stolida, the fourth on each side counting from without. In 

 S. hirundo the first secondary, the eleventh feather in the wing, is remarkable for its broad form, 

 and for being sinuously truncated at the end. This species also has three orifices on each half 

 of the oil-gland, whilst in S.fissipes I only found one. 



2. Jthynchops. From an examination of R. nigra and R. albirostris, LICHT., this genus 

 seems to have exactly the pterylosis of Sterna ; but the down-feathers appeared to be smaller, and 

 entirely deficient among the contour-feathers of the tracts. Both species have twelve tail-feathers 

 and from twenty-nine to thirty remiges, of which ten are seated on the pinion, and the first 

 is the longest. 



