NATURAL SCIENCES OF PHILADELPHIA. 27 



A skeleton of this species in the Museum of the Academy of Natural Sciences 

 was brought by Dr. Isaac I. Hayes, from Upernavik, Greenland, in lat. 74°. 



I was at first disposed to regard this as a young individual of one of the 

 species under observation, perhaps of B. a n g u s t a t a or d e c 1 i v i s. A very 

 brief study was sufficient, however, to reveal its manifold differences from 

 these. In cranial features it resembles most the B. d e c 1 i v i s, but I am sat- 

 isfied that no such difference in the form of the muzzle of the cranium as 

 obtains here can exist between young and adult of the same species. 



Beluga declivis Cope, Proc. Acad., Phila., 18G5, 278. 



This species resembles the a n g u s t a t a in the general proportions of the 

 cranium ; the muzzle is relatively shorter in the specimen, and its margins 

 decurved toward the end ; it therefore resembles also the catodon, which has 

 much less marked maxillary notches, a different prenarial space and shorter, 

 heavier mandible. The inferior view presents some analogy with that of the 

 B. r h i n d n, in the largely developed vomerine tablet ; but the palatines 

 are even further separated by an interval of three-quarters of an inch. The 

 horizontal palatal surface of these bones mark a narrow incurved longitudi- 

 nal process only, and they appear in the inferior half of the anterior wall of 

 the nasal meatus, as narrow strips lying next to the vomer. The pterygoids 

 are nearly exactly parallelogrammic, their exterior angles alone in contact 

 on the horizontal plane. The exposure of the premaxillaries extends, as in the 

 other species, to beyond opposite the fifth maxillary tooth. Of the superior por- 

 tion of the palatines the anterior portion extends to opposite the notch ; the 

 vertical portion of the posterior ala is broader than the horizontal. The mid- 

 dle of the palate is prominent without lateral angulation. The proportions 

 are explained by the following measurements. 



In. Lin. 



Length from end of muzzle to convexity of condyle 22 



"•j» " " " occipital crest 21 5 



'/ " " " nares 15 3 



« .. " " " maxillary notch 10 7 



" " •" foramen magnum to occipital crest 4 5 



"•" . of temporal fossa 7 



" '" orbit 2 8 



" , " ramus mandibuli 16 7 



<^ " gonys 2 9 



Breadth at distal two-fifths muzzle... 3 6 



'■ " notch of maxillary 7 7 



" " orbits 11 6 



" " frontal margins 



" of foramen magnum 2 



" " external nares 2 9 



" ■ between apices of paroccipital crests 9 



Teeth i^o 



The sella turcica is little marked, and the suture between the sphenoid and 

 presphenoid distinct, as indicated in the figure in Huxley's Elem. Compar. 

 Anat. 277. The teeth are relatively much smaller than in the concreta, and 

 the posterior but loosely attached to the alveohe, being principally held in posi- 

 tion by the palatal integument. The anterior above are considerably worn 

 on their inner faces. 



*The tympanic and periotic elements are much like those of the rhinodon, 

 and though the latter is known from a much smaller animal, its tympanic bone 

 is about the size of that of the former. The only noticeable difference is the 

 greater elevation of the prootic. 



The corresponding portions of the Beluga an gu s tat a are larger and consider- 

 ably heavier, though the cranium is a little less in all dimensions than that 

 of the d e c 1 i v is. The opisthotic process is more prolonged than in the 



1869.] 



