| OCR Text |
Show 887.] PROF. T. J. PARKER ON CARCHARODON RONDELETII. 29 % centim. From tip of snout to centre of eye 23 >» -i >. upper angle of nostril 22 " .. >, centre of mouth 30 » -> .. 1st gill-slit (dorsal end) 116 From centre of eye to spiracle 33 Width of mouth-aperture, in a straight line 58 Height of 1st gill-slit. 64 Width of flattened caudal region (vide infra), measured with calipers 42 Height of ditto, measured with calipers 18*5 Height of caudal fin from tip of dorsal to tip of ventral lobe 146 Height of dorsal lobe of ditto, measured along anterior border from root to tip 106 Height of ventral lobe, similarly measured 95 The skin is dark grey above, white tinged with pink below, the latter colour being evidently due to blood in the skin and not to the presence of any special pigment. The under surface of the snout is dark, not white and pink as in Smith's specimen. The snout is considerably less pointed than in Lamna, or than in the young specimen figured by Smith. The eye is also markedly smaller in proportion to the size of the head than in Lamna (cf. description and figures of skull, infra, p. 32 and Plates IV. and V. figs. 1-5 and 11). The form of the caudal region is remarkable, and is not adequately described in any of the books at m y disposal, in which it is merely stated that the tail is provided with lateral ridges. It is more correct to say that the tail for a short distance in front of the caudal fin is strongly depressed, so much so that its width is more than double its height, a transverse section having the form shown in fig. 19, Plate VII. It looks very much as if this curious modification must have the result of providing Carcharodon (and Lamna, in which the same structure obtains) with a combination of vertical and horizontal tail-fin, the latter-the flattened region just described-being developed as a means of enabling the fish to rise rapidly from great depths. 2. The Teeth. Only the central tooth of each row in each jaw is symmetrical, all the others having their long axes directed outwards. The exposed portion of the upper middle tooth (specimen C) is 4 cm. in height, and 3'7 cm. wide at the base. In the lower middle tooth these dimensions are respectively 3*4 (height), and 3*2 (width at base). In both jaws the outer surfaces of the teeth are markedly flatter than the inner. 3. The Skeleton. The vertebral column of Carcharodon has been fully described by |
