TUESIO PERONII. 79 



seem to me to beloug to tliis species. Oue of them (No. 20) is appar- 

 ently that meiitioucd by Schlegel under this species in the Ahhandlungen 

 (Heft I, p. 24). It most resembles PyoclelpMnusfroenatus. 



Judging from an authentic skull of i. borealis in the IsTational Museum 

 (presently to be described), I believe that there can be no reason tu 

 doubt the correctness of Professor Flower's identification of skull No. 

 3029 in the College of Surgeons. It is from Tasmania. The total length 

 is 44"". The triangular area in front of the nares is but slightly con- 

 cave. The iutermasilUe, which are much depressed, do not touch in 

 the median line; they are farthest apart at the distal extremity. The 

 central portion of the symphysis below is raised above the level of the 

 lower surfoce of the rami. The coronoid is high. The pterygoids, as 

 alread}^ stated, touch only at the tip. The palate is convex. 



All these charjacters are presented by the skull of L. borealis and are, 

 therefore, of no moment in distinguishing the two species. Indeed, I am 

 at a loss to find cranial characters by which to distinguish them, since 

 the proportions of the two skulls (seep. 82) are on the whole very much 

 the same. In the skull of L. pero)iii^ however, the temporal foss;iB are 

 relatively smaller, the mandible is shorter, its depth opposite the coro- 

 noid process is less, and it is less attenuated at the extremity. The right 

 intermaxillary bone in our skull of L. borealis ends proximally opposite 

 the middle of the nares, instead of running back to the posterior wall, 

 but this is very probably an individual variation. 



The skull figured in the Osteographie is also much like that of L. bore- 

 alis from California, but we know that the former is from south of the 

 equator, while, so far as I am aware, no porpoise having the coloration 

 of L. borealis has been observed in southern waters. It would appear, 

 therefore, that the two species are closely alike in cranial characteris- 

 tics, but widely dissimilar in coloration. 



Tiie figures of L.peronii given by D'Orbigny and Gervais (specimens 

 from Cape Horn) and Gray (specimens from midway between Cape Horn 

 and New Zealand) agree very closely, the chief difference being that 

 in the former the pectoral fin is represented as dark in the center of the 

 posterior margin. 



Lesson's figure (Voyage of the Goquille, pi, 9, fig. 1) represents a dol- 

 phin with white flukes and an elongated beak, which characters are also 

 mentioned in the text.* 



This may be a distinct species, though it is more than probable that 

 the figure is inaccurate. The measurements of the exterior given by 

 Lesson t differ much from those which I find in the notes upon L. bore- 



* Zoology, Voyage of the Coquille, i, pt. 1, p. 180. t L. c. 



