436 



ON THE PETRELS COLLECTED DURING 



very early, when the latter had only acquired the most prevalent of the 

 characters now existing in the various groups of that suborder. One 

 branch of this stock has since become greatly modified in the Tubinarial 

 direction, whilst the other branch, losing " B " and the large vomer, and 

 becoming desmognathous, split up and gave origin, at different times and 

 in different ways, to the remaining families of the group. The definite- 

 ness of the characters of these, and the amount of specialization they 

 show, indicate not only a great antiquity for the whole group, but also 

 the great amount of extinction that has gone on amongst its members in 

 the past, in the process of which nearly all the intermediate and less 

 specialized forms have disappeared. 



DIOMEDEINJE 



PROCELLARIID^E N 



PROCELLARIIN^E 



OCEAN ITID^E 



Exp. vol.iv] 

 pt. xi. pi. i. 



DESCRIPTION OF THE PLATES. 

 PLATE XII. 



1- Head of Oceanites oceanicus. 1 a leg and 1 b foot (from before) of same. 



2, 2 a, 2 b. The same of Garrodia nereis. 



3, 3 a, 36. The same of Pelagodroma marina. 



