OSSEOUS SYSTEM OF AVES. 



33 



of the ilia ; the seventh to the tenth vertebrae have no parapo- 



physes ; the eleventh to the fourteenth have them long and strong, 



thickest in the last. All 



these abutments, with the ^^ 



expansions from the neural 



spines, coalesce with the in- 



nominata and convert the 



pelvis into one complex 



mass of bone. 



The iliac, ischial, and 

 pubic elements are deve- 

 loped as distinct bones, but 

 speedily coalesce at their 

 point of junction around 

 the acetabulum and usually 

 elsewhere : their indepen- 

 dence is longest maintained 

 in the Cursores.^ Ossifi- 

 cation begins in each from 

 a single point, even in the 

 much elongated ilium of 

 Struthio and Dromaius. 

 This bone is, in fact, a 

 single vertebral element, 

 or rather part of one ; it is 

 homologous -with the pelvic 

 bone, 62, in figs. 43 and 

 101, D (vol. i.), and with 

 62 in fig. 28, p. 159, of my 

 work on the ^ Archetype 

 Skeleton' (cxL. vol i.), 

 where it is shown to com- 

 plete the pleurapophysial element of the pelvic haemal arch ; 

 the ischium being the hfemapophysis of the same arch. The 

 ilium in Birds, figs. 21 and 22, d, h, fig. 23, b, fig. 24, h, c, c\ 

 is remarkable for its developement in the direction of the 

 axis of the vertebral column, extending its connections with 

 many more segments than its own: it is accordingly long and 

 narrow, thickest midway, fig. 22,/, where it contributes the upper 

 wall of the acetabulum, ib. z, in front of Avhich, rZ, it is outwardly 

 concave ; behind the acetabulum, ib. g, U, it is convex. It differs 



Side view of pelvis, Eagle. 



VOL. II. 



' XLiv. vol. i. p. 267. Nc. 1386 



D 



