PEOFESSOR OWEN ON INDIAN CETACEA. 19 



"elongate, about \ the length"^; but the definition of the term of comparison being 

 omitted, whether it may be " length of the dental series," " of the mandibular ramus," 

 or " of the entire skull," detracts from my means of testing this osteological character, 

 whatever may be its value in regard to the variation in length of the " symphysis man- 

 dibulae" of the restricted Delphini of Cuvier's system. 



In the skull, no. 423, of the " Gadamu" (PI. IV.), the symphysis mandibulae (figs. 

 o& 4,5,5) is more than -jth the length of the entire dental series, and about ^th the 

 length of the entire ramus. 



Assuming, however, the section or subgenus of the present Dolphin to be Steno, it 

 then belongs to that subsection which is characterized as having the " ** £eak sepa- 

 rated from the forehead hy a cross groove"'^. 



In this section the present species differs from the Belphinus (Steno) malayanus in 

 colour, in number of teeth, and perhaps also in size. The D. malai/anus is " greyish 

 above and below;" the dental fovxaula, -^Q^^^lii. From the Belphinus (Steno) 



frontatus of the Indian Ocean, with teeth |i^=86 or |y^|y=84, I), gadamu differs 

 in the greater number of teeth. From Belpihinus (Steno) compressxis the present species 

 differs in the minor compression of the head, the shorter and less attenuated snout. 

 The B. (Steno) attenuatus. Gray, departs still further from B. gadamu in the length 

 and slenderness of the snout and the more numerous teeth, the formula being jq^, 

 = 160. 



In the skull of i*. (Steno) gadamu (PI. IV.) the maxillo-premaxillary part of the rostrum 

 is broader and lower than in B. (Steno) frontatus, the premaxillaries rise above the max- 

 illaries, at the middle of the rostrum, with a more abrupt transverse convexity, and the 

 maxillaries slope therefrom outward and less steeply downward to the alveolar border. 

 Behind the dental series the bony palate, there formed by the back part of the maxil- 

 laries, by the palatines, and pterygoids, forms a longitudinal bar convex across and 

 increasing in depth as it recedes ; the sides of the bar are continued into channels of 

 the same length, concave transversely, and impressing the sides of the posterior palatal 

 surface of the maxillaries. This undulating disposition of the bony palate subsides 

 opposite the penultimate or antepenultimate teeth, in advance of which the bony palate 

 is nearly flat, with a strip, 2 inches long, of the vomer at the mid line, and in advance 

 of this is slightly hollow transversely, or canaliculate. 



The sockets of the teeth are in contact, about 4 lines in diameter. In the skull 

 transmitted, and here noticed and figured (PI. IV.), 1 count 23—23 in the upper 

 jaw, and 27 — 28 in the lower jaw. The teeth have a long and large rounded base and 

 a short enamelled crown, slightly incurved, not very sharply pointed ; about ten anterior 

 alveoli are coextensive with the symphysis. 



' Zoology of the Voyage of H.M.S. Erebiis and Terror: " Cetacea." 4to. 1844, p. 43. Not any of the 

 figures of the skulls of Steno, Gray, illu.strate the symphysial character in question. In a specimen of Steno 

 frontatus in the British Museum the mandibular symphysis is about one-fourth of the entire length of the 

 skull. ' Ibid. 



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