No. 433-] 



CERTAIN GROUPS OF BIRDS. 



45 



Sir Richard Owen, who published a great deal about the 

 osteology of ostriches and their kin, both living and extinct, 

 says of the sternum of Strut/no came/us that " it is broader in 

 proportion to its length, and subquadrate in the ostrich," and 

 that in "all these keel-less sternums ossification begins, as in 

 the ostrich, by a pair of centers expanding until they meet and 

 coalesce in the middle line, and thence, according to the stimulus 

 of the growth and pressure of the pectoral muscles, extending, 

 as a keel, into the interspace." 1 



In the pelvis of Struthio the ilia are long and narrow, their 

 postacetabular portion being thoroughly and widely separated 

 from the ischium upon either side (Fig. i.), while in front the 

 preacetabular region is shorter and much concaved externally. 

 Huxley says: "In Struthio, alone, among birds, do the pubes 

 unite in a median ventral symphysis. Another, not less 

 remarkable circumstance, in the ostrich, is, that the 31st to the 

 35th vertebrae inclusively (counting from the atlas) develop 

 five lateral tuberosities. The three middle tuberosities are 

 large, and abut against the pubis and the ischium. In these 

 vertebrae, as in the dorsal vertebrae of Chelonia, the neural 

 arch of each vertebra shifts forward, so that half its base articu- 

 lates with the centrum of the next vertebra in front ; and the 

 tuberosities in question are outgrowths, partly of the neural 

 arch, partly of the juxtaposed vertebral centra, between which 

 it is wedged. Hence, in young ostriches, the face of each 

 tuberosity exhibits a triradiate suture." 2 



A conspicuous propubis is developed in the case of Struthio, 

 and this has been figured by Owen (Anat. Vert., Vol. II, p. 36, ;;/), 

 but in that figure the peculiar structure to which attention 

 was invited by Garrod is not shown ; this consists of a small 

 osseous plate attached to the pubis, that is partly surrounded 

 by cartilage. 3 Forbes speaks of " this paper, written in con- 

 junction with Mr. Frank Darwin," and points this out as the 

 principal point of interest, and refers to it as "a peculiar nodule 

 of bone lying on the center of the pubis and, in some respects, 



1 Anat. Verts, vol. ii, pp. 24, 25. 

 2/^V/.,pp. 251, 252. 



8 Garrod, A. H. Coll. Sci. Papers, p. 99. 



