296 PROCEEDINGS OF THE ACADEMY OP 



Length of symphysis mandibuli 1-25 



" temporal fossa 250 



Breadth between orbits 6*30 



' at notch 3 55 



" at middle of muzzle 3 - 38 



" of intermaxillary at middle 1-375 



From the above it will be seen that the nearest ally of this species is the 

 Delphinus (Lagenorhynchus} clanculus Gray, in which the muzzle is 

 considerably shorter and the cranium relatively longer and wider; that is, 

 length of cranium proper equal in the latter to the length of the muzz'e, and 

 breadth at orbits a little greater than either. Its form renders a distinction 

 between Lagenorhynchus and Delphinus improbable, on present bases. 

 Habitat unknown. Museum Smithsonian, No. 388(5. 



DELrHINCS PLAGIODON, Sp. 110V. 



A robust species of the subgroup Tursio, (Gray), with a strongly depressed 

 triangle extending but little in advance of the posterior tooth. It is in many 

 points allied to the D. d o r i s, but differs in the muzzle being compressed 

 rather than depressed, especially at the tip, the teeth fitting very closely and 

 compressed transversely to the jaw, scarce four in an inch; aiid from the 

 specimen of the Museum Salem, in having the mandible heavy and much 

 prolonged at the symphysis. The form is an approximation to Steno, but the 

 symphysis is short, nevertheless not more so than in St. tucuxi Gray. 

 Until other characters are educed it will not be possible to distinguish Steno, 

 Tursio, Delphinus and Lagenorhynchus as more than one genus. In this 

 view I support the already expressed opinion of Lilljeborg. 



Maxillaries much decurved, their elevation above the alveoli scarcely greater 

 than that of the premaxillaries above themselves. The latter form a very 

 strong rounded ridge, straight as far as visible in profile. Width at notch 

 two and two-third times in length. Prenareal part of triangle moderately con- 

 cave medially, with the term nal portion rugose. Supraorbital plates of 

 maxillary externally thickened ; in front of notch distinctly recurved. Ptery- 

 goids in contact, exteriork plane, inferior angle sharp, included depression 

 angulate. Vomer well displayed at middle of palatal face, not in contact with 

 maxillaries ; premaxillaries narrowly visible on the anterior half. Teeth 3< t 

 stout, occiput flat transversely, prolonged, rounded in profile, and not 

 acuminate, incurved. Supraoccipital crest rather weak. Measurements : 



in. 



Length to outline of occipital condyles 17 



" maxillary notch 9'80 



" of temporal fossa 3-1 



" upper tooth line , 8*25 



" ramus mandibuli 14-4 



" symphysis mandibuli 2 



Depth of cranial chamber 4'75 



Width at temporal crests behind 5-6 



" above orbits .. 7'25 



" at notch 3-55 



" at middle of muzzle 2-375 



Habitat is unknown. No. 3884 Mus. Smithsonian. 



This species resembles closely the figure of the D. doris given by Dr. 

 Gray in Zool. of Erebus and Terror, but does not at all agree with his descrip- 

 tion published in the Catalogue Cetaceans Brit. Mus., 1865, which applies 

 closely t the specimen described by me, Proc. Academy, 1865. As the crania 

 which have fallen under my observation are those of undoubtedly distinct 

 species, I have been at a loss which to regard as the true D. doris. I think 

 it would probably be more acceptable to the describer of the latter to regard 



[Oct. 



