Prof. Esch rich t on the Gangetic Dolphin. 179 



The upper and lower margin of the symphysis of the lower 

 jaw, viewed laterally, shows a gentle curve like the letter S ; 

 which is also the case with the upper jaw, though in a still less 

 degree, as shown in PI. V. In Guvier^s figure this curve is so 

 strikingly marked, that I am almost led to infer, that it may 

 have reference to the age or sex of the individual, especially as 

 Mr. Gray represents it equally marked (Catal. p. 352). Both 

 jaws project equally ; the lower scarcely perceptibly beyond the 

 upper. The anterior halves are about equally narrow, but from the 

 commencement of the posterior half the upper jaw projects about 

 1'" beyond the lower, as far as the anterior margin of the crests of 

 the upper maxillary bones (PL VII. fig. I), where the side branches 

 of the lower jaw begin to diverge. 



The palate stretches much farther back in the upper jaw, so 

 that the last pair of teeth do not meet the corresponding pair in 

 the lower jaw (PI. VII. fig. I m) . Notwithstanding this, the num- 

 ber of teeth in the lower jaw is, at least, equal to that in the up- 

 per, namely twenty-nine on each side ; while in the upper jaw 

 there are only twenty-eight on the left side. The teeth in the 

 jaws do not in consequence alternate in a quite regular manner, 

 the first pair in the lower jaw being anterior to that above ; the 

 1 7th being placed between the 16th and 17th pair above, 

 though close behind the 16th. Both the 18th and 19th pair 

 are between the 17th and 18th, and on the left side, the 

 31st and 22nd teeth stand between the 19th and 21st of the 

 upper jaw, while on the right side the 22nd and 23rd below 

 are between the 20th and 21st above; finally, the last (29th) 

 pair in the lower jaw occupies, on each side, the space between 

 the 26th and 27th pair in the upper. The length and form of 

 the teeth vary much, though not by sudden transitions. The an- 

 terior are of considerable length (as much as 9"'), pointed, and so 

 compressed and curved, that they have an anterior and posterior 

 surface, an anterior convex and a posterior concave margin. To- 

 ward the middle of the jaws they gradually become shorter and 

 cone-'shaped, so that the 1 9th lower, and the 21st upper pair 

 only project above the gums like little knobs, 1'" high, with 

 broad bases. They then become again somewhat larger, 

 especially in breadth. In proportion as they become shorter, 

 they recede from each other in each of the four rows, while 

 the two rows in each jaw approach nearer to each other; 

 especially in the upper jaw, where the 19th and 20th pair 

 come close up to the median line. In order, seemingly, to get 

 room, the teeth alternate here to such a degree, that the upper 

 21st on the left side, stands right between the 21st and 22nd on 

 the right, and this alternation continues quite backwards. In 

 illustration of this description a figure is given (PI. VI. fig. 2) 



12* 



