420 PROFESSOR OWEN ON THE OSTEOLOGY OF 



in different individuals of the Tr. niger are more marked than those above noticed in the 

 skulls of the two species, and induce me therefore to attach less importance to this cha- 

 racter as a specific one. In two skulls of adult males of the Troglodytes niger in the 

 College of Surgeons, the infraorbital groove as it passes backwards again becomes a 

 canal by the meeting, and in one specimen by the coalescence of the two sides of the 

 groove above the canal for an extent of from two to three lines before it enters the 

 sphenomaxillary fissure. Prof "Wyman indeed notices a similar conformation in an adult 

 cranium of the Chimpanzee belonging to Dr. J. C. Warren of Boston. Now this is a 

 more decided diflerence from the continuous open groove at the floor of the orbit in the 

 adult female Tr. niger than that groove presents in comparison with the shorter and 

 shallower one in Tr. Gorilla. I find too that the second character of Tr. Gorilla pointed 

 out by Prof Agassiz, — " from the internal walls of the orbits which recede from each 

 other in descending towards the floor, thus leaving a large pyramidal space for the lodge- 

 ment of the OS ethmoides," — is so much less marked in the female skull of Tr. Gorilla, 

 as contrasted with that of Tr. niger, as to induce me to view it more in the light of a 

 sexual than a specific modification. 



The 7th difference is a good character, and is repeated by each of the skulls of Tr. 

 Gorilla examined by me. All the skulls of Tr. niger also show the backward projecting 

 point, where the emargination exists in Tr. Gorilla. 



In regard to the 8th character, the minor relative projection of the incisive alveoli 

 beyond the line of the rest of the face is as characteristic of the three skulls of Tr. 

 Gorilla now in England as of the four in the United States, and results from the same 

 comparative shortness of the premaxillary bones, between the nasal orifice and the edge 

 of the incisive alveoli. But the ossa nasi, besides being more narrow and compressed 

 superiorly, are more prominent at that part in Tr. Gorilla than in Tr. niger, and they 

 are also more expanded and broader inferiorly, and I cannot but regard the most deci- 

 sive mark of the specific distinction of the Troglodytes Gorilla to be the longer persist- 

 ence of the maxillo-premaxillary sutures, and the evidence thereby given of the peculiar 

 form, development and connexions of the upper portions of the premaxillary bones. It 

 is remarkable indeed, since these sutures remain so distinct in the adult female skull 

 and in two of the adult male skulls in the Bristol Museum, that no trace of them should 

 have been detected in any of the four skulls taken by Dr. Savage to America, in which 

 Prof Wyman describes the ossa nasi as being ' ' firmly co-ossified with each other and 

 with the surrounding bones." 



The triangular expanded facial part of the upper end of each premaxillary intervening 

 between the nasal and maxillary bones will always serve to distinguish the cranium of 

 an immature Tr. Gorilla from that of a Tr. niger. 



