202 PROCEEDINGS OF THE ACADEMY OP 



less so than those of the D. euphrosyne and rniorops. The muzzle, 

 though convex in section, is more depressed than in any of the other species, 

 especially opposite the posterior extremity of the dental series. The acumi- 

 nate basal triangle extends an inch or more beyond this point. The prernax- 

 illaries are in one specimen quite continuous with the surface of the maxil- 

 laries ; in the other specimen, a slight groove marks the suture. The blow- 

 holes are rather small, and the nasal bones prominent. The breadth and de- 

 pression of the occipital region is the most striking feature. The temporal crests 

 are as. far apart as one-half the length of the muzzle measured in front of the 

 blow-holes, (in the variety b^low it enters two and two-fifth times,) and the 

 outline of the occiput between them nearly transverse. Its breadth is more 

 than double the height of the occipital crest above the foramen magnum, (one- 

 half in the variety.)" The frontal bones are broad and large ; the width at the 

 blow-holes enters the length of muzzle from the same point one and three- 

 fifth times ; in the variety very nearly twice. These differences are not 

 greater than occur in human skulls, yet it is probable that in a state of nature 

 they accompany other differences, which are together preserved isolated, indi- 

 cating the existence of species. The gutter between the occipital condyles is 

 narrow. In one specimen (596) the anterior basi-occipital suture is but little 

 concave; in the second, (595,) its sphenoid portion is a little distance be- 

 hind its pterygoid, while in the variety (499) the sphenoid encroaches 

 much more upon the occipital. In the latter, the supraoccipital crest is 

 slightly developed ; in asthenops, (595,) a larger individual, it is more 

 so, though slight ; in 596, neither it nor the temporal crest exist. In this the 

 muzzle is a little shorter ; it is evidently a younger individual of a larger 

 specimen than the variety. The following measurements will explain their 

 other features : 



595 596 



Length from notch to occipital condyle 5J in. 5| in. 



" " " to middle supraoccipital crest... 4| " 4| " 



" " " to end of muzzle 9i " 9 " 



Width of muzzle at notch 3 , (j in. 3 T <j in. 



" " at middle 2 If " 



" between outlines of frontal expansion 6f " 65 *" 



" " temporal crests 5f " 5 " 



" across blow-holes If " lj 



Length of gonys 1| 



m ..I 3 6 42 



Teeth ? 42 



The above measurements are to be understood as made in right lines. The 

 muzzle of the asthenops is less elongate, with the premaxillaries much 

 more depressed than Dr. Gray represents to be the case in his D. euphro- 

 ' syne, (Zool. Ereb. and Terror, t. 22.) and the number of the teeth is con- 

 siderably less than in his D. a 1 p e. The habitat is not known. 



The cranium representing the variety above mentioned may really belong 

 to another species. It differs from the e u p h r o s y n e in the longer triangle, 

 muzzle, and gonys, (and smaller number of teeth). It differs from our speci- 

 men of the styx in the smaller size, obsolete orbitosphenoid fossa, longer 

 triangle, and longer gonys. The last measures four-fifths of the width at the 

 notch : in the styx one-half or less. Habitat unknown ; from the Morton Coll. 



499 



Length from notch to occipital condyle 5| in. 



" " " middle of supraoccipital crest 4 



<( 



" " " endofmuzzle 9^' 



13 K 



Width of muzzle at notch 3g 



" " middle 1| " 



" between outlines of frontal expansions 5| ' 



" " temporal crests 5 



[Oct. 



