1885.] TROCHILTD.«5 CAPRIMULGID^, AND CYPSKLID.'E. 901 



this .ispect of the pelvis, which strikes one upon the first glance at 

 the hone. Two more ribs follow the pair borne l)y the I'Jth vertebra ; 

 (he first of these rceet the last pair of costal ribs below, while above, 

 their tubercula and cajiitula liave been so far absorbed that these ribs 

 look as if they were anchylosed to the outer margin of the ilium on 

 either side. The last pair of ribs neither meet the sternum below 

 nor the pelvis above, but are attached to the pair just described. 

 These ribs differ from the preceding ones in not developing epipleural 

 a|)peudages. This arrangement, it will be seen, gives 8 pairs of ribs ; 

 the first two pairs do not reach the sternum ; the next 5 pairs do, 

 meeting .5 pairs of costal ribs ; finally the last pair are in every sense 

 floating ribs. 



Through the 27th vertebra, the following segments are appro- 

 priated by the sacrum; then come 5 free caudals, making 32 vertebrae 

 in the spinal colnnni of this Humming-bird, the whole being finished 

 off by a comparatively large pygostyle, probably composed of several 

 others. 



The pi/c/osti/le is terminated in a peg-like point, and is not flat- 

 tened and quadrilateral as in the Swifts and many Passeres. 



Trochilus has a short and broad pelvis, being much compressed 

 from above downwards. Viewed from above, we find that the open 

 " ileo-neural grooves" are over the 18th and 19th vertebrae, the two 

 described above as anchylosing with the fore part of the sacrum. 

 This arrangement is rare among existing birds — unique so far as I can 

 recall at the present writing. The anterior and in-turned extremities 

 of the ilia are rounded points, meeting the outer sacral margins 

 just opposite the posterior endings of the ilio-neural grooves. The 

 parial foramina among the diapophysesof the urosacral vertebrae are 

 quite large. 



Professor Owen found them small in a specimen o{ Trochilus pella} . 



Upon a lateral view we observe that the narrow ilium is much 

 concaved immediately anterior to the cotyloid cavity ; its outer margin 

 forming a part of the long gentle curve completed by the postpubis, 

 which latter projects far behind where it is turned upwards. No 

 propubis is developed. 



The acetabulum, ischiac, and obturator foramina present nothing 

 of marked interest; they have all an average size and are in due pro- 

 portion with the surrounding parts. 



The obturator foramen is thoroughly closed in by the ischium, 

 after which this bone arches over an obturator space, to meet the 

 postpubis again in a little foot-like process. 



In many birds a notch on the hinder border of the pelvis denotes 

 the landmark between ilium and ischium in this situation. No such 

 feature exists in Trochilus, this Humming-bird having in the posterior 

 portion of its pelvis much to remind u? of similar parts of the skeleton 

 in the Passeres. 



The sternum (figs. 3 and 6, Plate LX.)- — So far as its general form 

 and characteristics go, the sternum in the Hummers has long been 

 known to us, and this information has been principally derived from 

 1 ' Anat. and Phys. of Vert.' vol. ii. p. 32. Loud. 1866. 



