370 CETACEA. 



Description of external features (PI. XXT, fig. 4). — The head is convex from 

 the blow-hole to the upper lip, but its sides immediately before the angle of the 

 mouth are somewhat anteriorly convergent, but rounded (fig. 5). The gape poste- 

 riorly has a long upward curve. The eye which is well developed, is near the angle 

 of the gape, and in the adult is placed about one inch above it, with a slightly 

 downward slope. The ear is nearly on the same level as the angle of the mouth, 

 and it is extremely small, crescentic, and not measuring more than 0"*12 in diameter. 

 The posterior margirf of the blow-hole is immediately behind the anterior angle of 

 the eye. The blow-hole (fig. 5) is crescentic and unsymmetrical, being more to the 

 left than to the right side. There are two slight eminences about one inch behind 

 the blow-hole. The constriction of the neck occurs below the ear and slightly be- 

 hind it. The pectoral flippers have their bases nearly on a level with the tip of the 

 snout, and they are triangular structures moderately long and broad ; the breadth 

 equalling about one-half their length. Their anterior margins describe a gentle 

 outward curve to the tip of the second finger ; their greatest breadth is attained at 

 the extremity of the 5th digit, on the proximal side of which their posterior margins 

 rapidly contract. The centre of the dorsal fin is situated behind the middle of 

 the body, taking the caudal notch as the hindmost limit of the animal. The 

 fin is falcate and curves upwards and backwards to a rounded point, below which 

 tlie posterior margin is concave. Erom the base of the dorsal fin posteriorly to the 

 caudal notch the median line of the back is sharp. The ventral line is also sharp 

 for some inches behind the anus. The dorsal and ventral ridges stop short about 

 five inches from the caudal notch. The caudal flippers are moderately broad with 

 their posterior margins concave from behind forwards. The mammary slits (PI. 

 XXXIII, fig. 1, m.) occur on each side of the vaginal orifice at a distance from each 

 other of 2*75 inches. They are unsymmetrical in position, the left being placed 

 further away from the vagina than that of the right side. The mammary slits are 

 about one inch in length, and the nipple of each is almost completely hidden in its 

 own furrow. Each nipple is about a quarter of an inch long and laterally com- 

 pressed, the orifice occurring on the external side of an apical crenated ridge. The 

 vaginal opening (fig.l, ^.) is 3*25 inches long, and is separated from the anus (fig. 1, a.) 

 by a distinct perineal interval (fig. \pe.) 1""50 in longitudinal extent, an interval 

 which does not apparently exist to the same degree in Cetaceans devoid of pelvic 

 bones. 



The skin above, generally, is dark slaty-blue, nearly black, and very little paler 

 on the ventral surface. None of the specimens that have come under my observa- 

 tion have ever presented those scratch-like streaks on the skin which I have referred 

 to as occurring in 0. fluminalis. The young have a distinct moustache occurring 

 about one-half inch above the upper lip, and consisting of five brownish bristles ; 

 the first bristle being placed about one inch behind the tip of the snout, the line 

 of bristles occupying an area of three-quarters of an inch (Plate XXXIII, fi.^. 1, h). 



The foregoing description was drawn up from a gravid female, the foetus of 

 which (fig. 1) was nearly fully mature on the 1st June, the date of the death of the 



