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Show 1883.] PROF. FLOWER ON THE DELPHINID^E. 489 (Steno 1) gadamu of Owen1, described from a mutilated skull and a native drawing of a specimen taken at Vizagapatam (Madras) in 1853. The skull is now in the British Museum; it is that of a young animal. The pterygoids are widely divergent. The rostrum is wider and more depressed than in D. sinensis; the premaxillae especially are of a peculiar form, being narrow at their upper third and enlarging at the middle of the rostrum, where they are both more elevated and wider than in other species. The teeth are OQ OQ 2^28 according to Owen. A more complete skull of the same species, from Australia, has been recently added to the Cambridge University Museum. D. lentiginosus, Owen, from the same locality, described in the same memoir, is a closely allied species, if distinct. Delphinus plumbeus, Dussumier, in Cuvier's ' Regne Animal,' 2° edit. t. 1, p. 283 (1829), according to the skull in the Paris Museum, figured by Gervais (Osteographie, pl. xxxvii.), represents the longest and narrowest form of this type, with the most numerous OQ teeth, viz. ~, only 4 mm. in diameter. The pterygoids are very characteristic. It is a large species, the skull measuring 550 m m. in length. This has been conjecturally identified with D. malayanus, Lesson (Voy. de la Coquille, Zool. p. 184, pl. ix. fig. 5 (1826), from external form only). LAGENORHYNCHUS. Lagenorhynchus, Gray, Zool. Erebus & Terror, p. 34 (1846). The following characters appear to be common to all the animals of this section of which the complete osteology is known :- Cranium without grooves on palate. Rostrum scarcely exceeding the length of the cranium, broad at the base, and gradually tapering towards the apex, depressed. The pterygoid bones rather short and broad, united in the middle line (see fig. 8, p. 490). Symphysis of mandible short. Teeth small, not exceeding 4 m m . in diameter, not numerous, 23-33. Vertebrae very numerous, 80 to 90. Spinous and transverse processes of the lumbal* vertebrae very long and slender. Manus with broad, flattened metacarpals and phalanges, with parallel borders. The skulls of the species assigned to this group vary considerably in form. L. albirostris especially deviates from the others in the outline, as seen from above, being more regularly pear-shaped, an appearance caused mainly by the anteorbital prominences of the maxilla, frontal and jugal, which stand out on each side behind the notch, being softened off and the rostrum tapering gradually to a sharp apex ; while in L. electra (also a large species) the prominences are more strongly developed, and the rostrum is more obtuse at the apex. The smaller L. acutus and L. clanculus are somewhat intermediate, the former, however, inclining strongly to the electra type, the latter to that of albirostris. Gray appears to have recognized this difference, although, as usual,"not defining it clearly, for in the 'Synopsis' (1868) he places 1 Trans. Zool. Soc. vol. vi. p. 17. |