OCR Text |
Show 140 DR. C. I. FORSYTH MAJOR ON THE [Feb. 19, Loris. Five specimens examined.-The lacrymal appears neither inside the orbit nor on the face. In front of the orbit there is a "fossa," entirely encircled by the maxilla. The crista posterior is also formed chiefly, in one case (Br. M . N o . 67 c, left side) entirely, by two processes of the maxilla, which in the latter instance unite on the orbital margin, above the os planum, and are always continued forwards into the fossa. In most specimens these two processes are separated on the orbital margin by a minute process of the planum, which therefore partakes in the formation of the crista posterior. In the anterior part of the fossa-where the latter, being roofed over by the maxilla, has become the canalis- may be seen a thin bone which is either the free termination of the reduced lacrymal, covered by the maxillary in the anterior part of the fossa, or, may be, the termination of the os Text-fig. 40. Text-fig. 41. Text-fig. 42. Text-fig. 40. Orbital region of Loris gracilis (Br. M . No. 48.10.31.3), about nat. size. Text-fig. 41. The same of Nycticebus tardigradus (Br. M . No. 96.11.29.4), about nat. size. Text-fig. 42. The same of Loris gracilis (R. Coll. Surg. Lond. No. 290), about I nat. size. (Lettering as in text-fig. 26.) planum. In one specimen (Br. M . No. 67 d) the process of the planum can be traced from the crista posterior forward to the anterior end of the canalis; in the absence of very young specimens it cannot be decided whether this anterior portion is the much reduced lacrymal united by synostosis with the planum, or the planum itself. In a specimen from the collection of the ltoyal College of Surgeons (No. 290), the condition displayed on the right side conveys the impression that the thin bony plate, visible in the canalis beneath the maxillary roof, is in fact the lacrymal. On both sides of the skull the planum creeps up on the orbital margin and separates the frontal from the maxillary, the former bone in this specimen partaking medially in the formation of the margin. In front of the os planum, a lateral and a medial process of the maxillary unite |