1899.] OSTEOLOGY OT THE TTTETNAEES. 401 



In Majaqueus and Diomedea exulans, for instance, tbe 2nd phalanx 

 of digit II. exceeds that of the 1st. Phalanx i. of digit I. is equal 

 in length to that of phalanx i. digit II. In Diomedea again it is 

 rather less instead of equal. In the smaller Petrels the elongation 

 of these phalanges is not so marked. 



ix. The Pelvic Limb. 



The bones of the pelvic limb are non-pneumatic ; the tibio-tarsus 

 is characterized by an enormous flabelliform ectocnemial crest 

 which rises high abo\e the articular surface for the femur: is 

 markedly inflected at its distal end, and provided with an ossified 

 extensor bridge. The fibula does not extend more than | the way 

 down the leg, and is much reduced in thickness distally. The tarso- 

 metatarsus has a well-marked intercondylar tubercle. The 

 hypo-tarsus is complex iu the Procellariidse and simple in the 

 Diomedeidse. The outer and middle toes are of equal leugth. 



In one skeleton of Biomedea exulans I find an ossified tarso- 

 metatarsal extensor bridge on the right foot. The hallux is repre- 

 sented by a metatarsal and an ungual phalanx, the latter often of 

 considerable size. Iu Pelecanoides it is absent. The femur, as a 

 rule, is about as long as, or less than, the tarso-metatarsus, and is 

 about half as long as the tibio-tarsus ; in Oveanites, Pelagodi-onia, 

 Cymodroma, and ProceUaria tlie femur shortens conspicuously, these 

 measurements being about -L as long as the tarso-metatarsus and 

 ^ as long as the tibio-tarsus. 



X. Eesults. 



Briefly, I think, the outcome of this paper has been to confirm, in 

 a large measure, the conclusions of Porbes as set forth in his most 

 A'aluable Report on the Petrels collected during the ' Challenger ' 

 Expedition (5). The appended diagram (fig, 2, p. 402) is a modi- 

 fication of that published by him in that work. He divided this 

 suborder into two families^ — ProcellaeiidjI; and Oceanitidje; 

 and two subfamilies — Peocbllaeiin^ and DiOMEDEiwiE. Pele- 

 canoides he regarded as an aberrant genus of the first mentioned 

 subfamily. 



I propose to make two Families — the Peocellaeiii)^ and the 

 DiomedeiDjE ; the former being further divided into two sub- 

 families — PROCELLAEirN"^ and Pelecanoidin^. Thus Porbes's 

 DioMEDEiN^ becomes raised to the rank of a family, his genus 

 Pelecanoides to the rank of a subfamily, whilst his family 

 OcEAKiTiD^ becomes, in my scheme, reduced to a section of the 

 PEOCELLAEiiNiE. The sectious in this subfamily are three in 

 number, and can quite conveniently be diagnosed from the 

 characters of the skull alone (see Keys, pp. 403-409). 



Pelecanoides forms the second subfamily. In the great width 

 of the basitemporal region of its skull it differs from every other 

 member of the suborder. The sternum and pectoral girdle are 



