1222 THE CETACEANS 



triangular or ovate, and, except in one species, the flippers have a characteristic 

 elliptical form. The coloration is black above and white below; the white of the 

 under parts terminating posteriorly in a trident-shaped form, with the lateral prongs 

 of the trident extending obliquely upward on the sides. The total length of Heavi- 

 side's dolphin is about four feet; the number of teeth being from twenty-five to thirty. 

 The white-fronted dolphin (C. albifrons), from New Zealand, is a rather larger spe- 



HEAVISIDE'S DOLPHIN. 

 (From True, Bulletin of the U. S. National Museum, 1889.) 



cies, with thirty- one teeth on each side. Nothing seems to be recorded as to the 

 habits of these species. 



THE IRAWADI DOLPHIN 

 Genus Orcella 



The upper waters of the Irawadi river are tenanted by a rather large dolphin 

 or porpoise {Orcella fluminalis) , which, together with a closely allied species, or va- 

 riety (O. brevirostris) , from the Bay of Bengal and its estuaries, as well as Singapore 

 and Borneo, constitutes a distinct genus. These dolphins are characterized by their 

 globe-like head, without beak, and their comparatively few and small teeth, which 

 occupy nearly the whole length of the jaws, and number from thirteen to seventeen 

 in the upper, and from twelve to fifteen in the lower jaw. In form the teeth are 

 conical and pointed, and they are set close together; those in the front of the jaws 

 of old animals being directed outward. The back fin is small and hook-like, while 

 the flippers are of moderate size, broad at the base, and subovate in form. These 

 dolphins attain a length of from seven to seven and one-half feet, and are of a slaty 

 or blackish color. In the Irawadi dolphin the color is pale slate above and whitish 

 below, with numerous irregular streaks on the sides; but in the one inhabiting the 

 Bay of Bengal the color is uniformly blackish without any streaks. The latter form, 

 whether it be specifically distinct from the dolphin of the Irawadi, or merely a va- 

 riety, appears never to ascend the rivers beyond the distance influenced by the tides, 

 while the Irawadi dolphin never descends to the estuaries. 



The following account of the habits of the Irawadi dolphin is taken 

 from Dr. J. Anderson, who writes that it " has much the character of 

 its marine fellows, being generally seen in small schools, which t frequently accom- 

 pany the river steamers, careering in front and alongside of them as is the custom 

 of the dolphins of the sea. Occasionally, however, a solitary individual may be ob- 

 served, but this is the exception, as two or three are usually associated together, 



