400 Ma. w. p. PTCKAFT OK THE [Mar. 21, 



viii. The Pectoral Limb. 



The character of the wing is very uniform throughout the 

 group. It is perhaps most nearly comparable to that of the 

 Laridse. It may be distinguished from that of this last group by 

 the absence of a groove for the deltoideus minor, and in that the 

 1st phalanx of digit II. is not fenestrated. 



The humerus in the Procellariidaj has the shaft dorso-ventrally 

 depressed. The free edge of the pectoral crest is triangular, the 

 caput huuieri is low and not sharply defined ; the tubercuium 

 inferius is large ; the sub-trochanteric fossa is of moderate size, is 

 single (not bipartite as in the GruUs), and does not receive 

 pneumatic apertures. The coraco-humeral groove is very shallow. 

 The crista inferius small. The ectepicondylar process is very 

 long. The supracondylar depression for the brachialis inferior is 

 moderately large and deep, but less so than in the Lari, in which it 

 forms a very deep pit, saved only from fenestration by a very 

 delicate floor of bone. 



The dorso-ventral flattening of the wing is very marked in 

 Puffinus, and the supratrochlear depression is shallower than in 

 the more typical humeri, such as those of Majaqueus and Friqfinus. 

 The shaft is almost cylindrical in the smaller Petrels belonging to 

 sections A, B of this paper. The ectepicondylar process is not 

 well developed, and the supratrochlear depression is shallow. 



The relative proportions in the length of the arm, forearm, and 

 manus vary considei'ably amongst the different genera, too much 

 so to be of use for systematic purposes. All the segments appear 

 to be sube(jual in Ptiffiims, some species of (Estrelata, Priocella, and 

 Fulmarus ; the manus is longest of the three in Thalassoeca, 

 Puffinus assimilis, and (Estrelata neglecta ; it is shortest in Majaqueus 

 and Dajption. 



In Pdi'canoides the pectoral crest is feebly developed, straight 

 and scarcely raised above the level of the shaft. The crista inferior 

 is deeply hollowed distad, and the ectepicondylar process and 

 supratrochlear depression are obsolescent. 



In the Diomedeidse — e. g. D. exulans — the proximal end of the 

 humerus is squarely truncate. The tubercuium inferius widely 

 separated from the caput humeri. The crista inferior has its free 

 edge swollen into a thick lip immediately before entering the 

 shaft. The subtrochanteric fossa is very small and receives 

 numerous pneumatic foramina. The supratrochlear depression is 

 shallow, inverted-pyriform, and extends some distance up the shaft. 

 The depression proximad of the ulnar condyle is i-elatively deeper. 



The forearm can be distinguished from that of the Lari by the 

 absence of distinct tubercles for the quills, and the presence of a 

 more or less deep and elongated groove in the infei'ior aspect of 

 tlie ulna lying in front of the inferior glenoid cavity. 



The manus in all cases, save apparently sections A, B of the 

 Procellariinte, can be distinguished from the Lari by the great 

 length of the terminal phalanges. 



