^6 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. [1H85. 



merous near the median line, but only visible on close inspection. Tlie 

 dorsal fin is tipped with white. Eye blackish. 



Head sloping. Lower jaw protruding slightly beyond the upper. 

 Dorsal fin moderately high and falcate, its front edge furnished with 

 five faintly-marked rugosities. Pectorals as in P. communis. Dorsal 

 and ventral margins of the body, between the vent and the origin of 

 the flukes, raised into a prominent thin ridge. 



Skull as in P. communis^ but the beak relatively shorter, and the 

 temporal fossie smaller. The maxillaries are also shorter proximally, 

 and the mandible less deep between the coronoid process and angle. 

 JS^umerous other differences of proportion will be found upon examina- 

 tion of the table on p. 98. The symphysis mandibuli is prolonged an- 

 teriorly into an obtuse point. Teeth §|, very small. The crown meas- 

 ures .065 by .05 inches, and is compressed as in other Phocsenas, though 

 in a less degree; the margin is not indented. 



Vertebral formula as follows : C.7; D. 14 (or 15*); L.27; Ca. 49=97 

 (or 98). All the cervicals united, as are also the last four caudals. 

 First thirty caudals with chevron bones. 



The pectoral corresponds closely to that of P. communis. Five car- 

 pals are present. The formula of phalanges is as follows: I, 1 ; II, 0; 

 III, 4; IV, 2. The two distal phalanges of fingers 2 and 3 and the 

 outermost of finger 4 are very imperfectly ossified. 



I deem it eminently fitting that this species should be dedicated to 

 my friend, Mr. William H. Dall, not alone on account of his prominence 

 as a zoologist, but also because the specimens and notes from which 

 the description has been drawn are the fruits of his labor. 



COMPARISON OF PHOC^NA DALLI WITH OTHER SPECIES. 



The three main features in which P. Dalli diffei's from the remaining 

 species of the genus are («) the coloration ; [h) the shape of the dorsal 

 fin ; and {e) the number of vertebrae. In all these characters it shows 

 an approximation to the species of Lagenorhynchus. 



In P. sj)i7ii2nnnis we have, according to Burmeister, a species which 

 is entirely black. P. communis and P. lineata, on the contrary, are 

 dark or black upon the upper or dorsal surface of the body, and white 

 or light upon the lower or ventral surface, the two opposite colors grad- 

 ing into each other on the sides. The coloration of P. Dalli differs from 

 both these styles in that the white or light area is confined to the pos- 

 terior half of the ventral surface, and is sharply defined from the sur- 

 rounding black color. 



In his recent admirable paper upon the Delphinidw (Proc. Zool. Soc, 

 1883, J). 505), Professor Flower recognizes the triangular shape of the 

 dorsal fin as among the salient characters of the genus Phocxcna. Its 

 shape is such in the species hitherto described, but in P. Dalli the tip is 

 recurved, and the posterior margin concave, giving the fin approximately 



*One dorsal vertebra was crushed by the harpoon. 



