1887.] PROF. T. J. PARKER ON CARCHARODON RONDELETII. 29 



centiin. 



From tip of snout to centre of eye 23 



,, ,, „ upper angle of nostril 22 



„ „ „ centre of mouth 30 



„ „ „ 1st g;ill-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 my 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 



