76 PROFESSOR OWEN ON THE OSTEOLOGY OF 



the skull under description, in which, as in the Gaboon variety, there is neither super- 

 orbital foramen nor groove. 



It would at first seem probable that the greater development of the lambdoidal and 

 sagittal cristas, to which the greater extent of the cranial part of the skull depends, in 

 the specimen from the river Danger, might be due to the greater age of the individual, 

 and the longer continuance of the stimulus of the action of the muscles concerned in 

 the support of the head, and in the movements of the anteriorly produced and prepon- 

 derating jaws. But the condition of the grinding surface of the teeth (PI. XXVI.), and 

 more especially that of the sutures (PI. XXVII. s, 27 and 11, 15 and 22), negative the idea 

 of the skull of the Gorilla from the river Danger having belonged to an older animal 

 than those skulls of the Gorilla from the Gaboon with which it has been compared. In 

 fact, in no other skull of the adult Troglodytes Gorilla that has hitherto been described, 

 is the course and extent of so many sutures more clearly traceable than in the present 

 specimen. 



The whole circumference of the partially coalesced nasal bone (PI. XXVII. is) is 

 shown by a suture which is as wavy or dentated as most of those in the Human cranium. 

 The two nasal bones are quite blended together at their upper or interorbital halves, 

 which form the usual well-marked ridge-like prominence characteristic of the species. 

 Above this ridge the bone expands and again contracts as it ascends, and terminates in 

 a point within three lines of the summit of the superorbital ridge. The remnant of the 

 straight suture which divided the lower halves of the nasals is confined to the anterior 

 surface of those bones. The strong and dense plate of bone (PI. XXVIII. is) sent back 

 to join the interorbital part of the frontal {ib. 11) comes off from the middle line of the 

 upper two-thirds of the nasals, is of a triangular form, and increases in breadth to its 

 lower border, which measures one inch three lines in extent. 



The suture of the upper expanded part of the premaxillary (PI. XXVII. 22'), which 

 is wedged between the nasal (is) and maxillary (21), and forms the upper and lateral 

 boundary of the nostril, is very distinctly marked, and is continued down to within an 

 inch of the alveolar border between the canine and outer incisor : the premaxillary 

 suture on the inner surface of the nostril (PI. XXVIII. 22") is continued into the 

 outer one about nine lines below the nasal bone, and so insulates the upper end of the 

 premaxillary. This variety does not exist in the skulls of the Gaboon Gorillas which 

 I have compared, and may be accidental to the individual from the river Danger. The 

 extent of the premaxillary in some young specimens of the Troglodytes Gorilla plainly 

 demonstrates the homology of the separated portion of the premaxillary in the present 

 adult, and saves the invention of a name for a bone, which otherwise might be deemed 

 to deserve such sign of a new and superadded part. 



The squamosal (PI. XXVII. 27) unites with the frontal (n) by a dentated suture more 

 than an inch long, separating the alisphenoid from the parietal to the same extent. 

 The suture between the squamosal and ahsphenoid is also dentated ; that between the 



