314 



Mr. P. R. Lowe on the Osteology of the 



dissection of one of the embryos of Chionarchus taken on 

 Kerguelen during the voyage of the 'Challenger* in 1874. 

 I have since been able to do this, and the results as regards 

 two points, at least, in regard to the osteology of the 

 skull seem to be sufficiently interesting as to be worthy of 

 record. 



The exact age of the embryo selected is, of course, 

 impossible to determine; but, as far as I could judge, it was 

 not much more than half-developed towards the point of 

 hatching. At any rate, it was considerably smaller than 

 other erabryos taken from the egg. 



Text-figure 7. 



7ac 



Portion of the skull of an embryo Chionarchus "minor" from Kerguelen, 



A. From above. B. From below. 



fr., frontals ; lac, lacrymals ; nas., nasals ; n.p. ofpmx., nasal process of 



premaxillse; i.sp/^.r., basisphenoidal rostrum; b.t.pl., basi-temporal 



plate. 



(1) After a little careful dissection, the quadrates, ptery- 

 goids, and palatine plates were exposed, and the first, and 

 probably the most interesting, point to be discovered was 

 that, contrary to what obtains in the adult bird, a very dis- 

 tinct and obvious basipterygoid process was demonstrated, 

 projecting from either side of the basisphenoidal rostrum. 

 The distal extremities of these two processes were apparently 

 coated with a cartilaginous articular surface, while, corre- 

 sponding with these two articular surfaces, two very distinct 



