| OCR Text |
Show 400 MR. W. P. PYCRAFT ON THE [Mar. 21, viii. THE PECTOBAL LIMB. The character of the wing is very uniform throughout the group. It is perhaps most nearly comparable to that of the Laridae. 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 Procellariidas has the shaft dorso-ventrally depressed. The free edge of the pectoral crest is triangular, the caput humeri is low and not sharply defined; the tubercuium inferius is large ; the sub-trochanteric fossa is of moderate size, is siugle (not bipartite as in the Gulls), and does not receive pneumatic apertures. The coraco-humeral groove is very shallow. The crista inferius small. The ectepicondylar process is very loug. 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 Priofinus. The shaft is almost cylindrical in the smaller Petrels belonging to sections A, B of this paper. The ectepicondylar process is not Avell developed, and the supratrochlear depression is shallow. The relative proportions in the length of the arm, forearm, and manus vary considerably amongst the different genera, too much so to be of use for systematic purposes. All the segments appear to be subequal in Puffinus, some species of CEstrelata, Priocella, and Fulmarus; the manus is longest of the three in Tlialassceca, Puffinus assimilis, and CEstrelata neglecia; it is shortest in Majaqueus and Daption. In Pelecanoides the pectoral crest is feebly developed, straight aud 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 Diomedeidas-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 relatively 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 inferior aspect of the ulna lying in front of the inferior glenoid cavity. The manus iu all cases, save apparently sections A, B of the Procellariinas, can be distinguished from the Lari by the great length of the terminal phalanges. |
