28 PEOF. G. B. HOWES AJS T D ME. H. H. SWINNEETON ON THE 



rightly records a transverse disposition of the first and second and the forwardly-directed 

 one of those Avhich follow (loc. cit. p. 606). In attributing the first cervical rib to the 

 fourth vertebra he was in agreement with Owen, who first discovered this 1 . Baur, 

 however, later described in an individual specimen the presence of a free rib upon the 

 third vertebra, and showed at the same time that (86 c . p. 736) the so-called caudal 

 " transverse processes " of the adult represent co-ossified ribs. Osawa (98 a . p. 485) 

 declares his inability to confirm the presence of the latter ; but, with Gadow, we can 

 do so, and can confirm the occasional presence of a rib to the third praesternal vertebra. 

 Neither Gadow nor Baur state the number of caudal ribs observed. Our own investi- 

 gation shows them to be present (PI. I. fig. 12) for at least the eight anterior caudal 

 vertebrae. Posteriorly to these, according to Giinther, the " transverse processes " 

 become rudimentary, and we have no material to prove whether they do or do not 

 ossify separately. The osseous rib-formula may accordingly now be rendered as 

 follows, allowing for the possible presence of additional caudal ribs yet to be 

 discovered : 



Prsesternal 5-6 



Sternal 3-4 



Poststernal 13-14 



Sacral 2 with variation. 



Caudal 8 observed at Stage S. 



Average 33 



In the adult animal the anterior prsesternal ribs alone stand related to both inter- 

 vertebral and vertebral bodies (cf. PL II. figs. 1 & 2), the rest either articulating or, as 

 in the case of the caudal and apparently in individual cases of the last three post- 

 sternal, becoming co-ossified with the vertebrae alone. Baur, in describing the prae- 

 sternal ribs, has drawn attention to the existence of supposed ligamentous homologues 

 in relation to the first and second vertebral segments, and to the third where an osseous 

 rib is absent. Of these ligaments, he describes the first as single-headed and attached 

 to the first intercentrum, the second and third as double-headed and attached to both 

 intercentrum and transverse process of their corresponding vertebrae (i. e. those behind), 

 and he points out that in its attachment to the intervertebral body the lower liga- 

 mentous tract agrees with the capitulum of the rib borne upon the fourth vertebra, 

 which he, with Owen and Giinther, describes as two-headed. Of the fifth rib, he 

 rightly points out that it is the capitulum which is reduced, wherefore it follows that if 

 his identification of these ligamentous tracts as vestigial ribs is correct, the first and 

 fifth are diversely modified. 



We can confirm (cf. PI. II. fig. 2) the general accuracy of his description and 



1 Owen, K. : Cat. Osteol. Series E. Coll. Surgeons Mus. vol. i. 1853, p. 142. 



