368 



DE. E. W. SHUFELDt's MOEPHOLO&TCAL 



find a spindle-formed figure produced, which is characteristic of 

 the Cypseli. 



In Swallows the bifurcation does not take place until the 

 spinal tract arrives nearly at the middle of the back, and then the 

 ends of the fork fail to join the rump-tract below. 



Now in Humming-birds, and I have examined a great many 

 excellent specimens of them, the " spinal tract " is altogether 

 different from this, for it consists of a very broad, lozenge-shaped 

 figure, spreading out over nearly the entire dorsal region, being 

 prolonged in a wide nuchal strip which merges with the " capital 

 area" anteriorly, while its low^er angle rests upon the uropygial 

 gland, and laterally spreads over the femoral region. Mesially, 

 and in the middle of this lozenge-shaped area, we have a short 

 longitudinal naked strip, but not nearly so conspicuous as it 

 is in the Swifts. 



Indeed, the pterylography of a true Cypselus and Trochilus is 

 as different in character as any two forms of birds can w^ell be in 

 this particular; and if one, unprejudiced in mind,'will look at 

 plate iii. of Nitzsch's work, there will be seen a greater similarity 

 between the dorsal tracts of Cypselus apus and Coracina cepha- 

 loptera than between Cypselus apus and Trocliilus moscliitus. 



"We are already aware that, notwithstanding Swifts and 

 Humming-birds possess the same number of primaries and rec- 

 trices, it rather conveys the impression that this is more a matter 

 of chance, when w^e find that they essentially differ in their ptery- 

 lography and in the number of secondaries in their wings. 



For another external character in the Swifts, and a very 

 excellent one, which I have failed to find elsewhere described, 

 we must turn to the integuments covering the pinion. Here we 

 find the entire skin exclusive of the border surrounding this part 

 of the limb, and on both sides, of a deep hlaclc colour^ being pro- 

 duced by a pigmentary deposit in the skin itself This peculiar 

 character is present both in Micropus and Chcetura, while it 

 is entirely absent in Trochilus. Swallows also lack this pig- 

 mentary deposit in the skin on both surfaces of the pinion. 



To conclude this chapter, then, I will make a few comparisons 

 between the external forms and characters of Micropits — a true 

 Swift — and Trochilus platycercus — a typical Humming-bird. 



So far as the general form of these two birds is concerned, a 

 glance at PL XXIV. figs. 37 and 39, will be sufficient to convince 

 any one that they are as different as tliey can tvell be. 



