g^ THE OSTEOLOGY AND MYOLOGY 



to almost its simplest expression. Vomer with the olfactory sense-capsule (ethmo-turbi- 

 nal); but the coosification is not perfect throughout. A spongy bone ("inferior turbinal") 

 is attached to the inner surface of each maxilla. 



The special characters of each of the bones above mentioned are now to be examined. 



The hasioccipital is only seen as a distinct bone in very young animals, although 

 traces of separation from the neurapophyses persist during adolescence. ^ Thus I find 

 the suture, in an animal three-fourths grown, extending from the side obliquely inward 

 and backward to the condyles, and exhibiting the part taken by the bone in the forma- 

 tion of the latter (about one third). The precondylar foramen is developed in, or just 

 to, one side of this suture ; another smaller opening exists a little internal to the last. 

 The connection of the bone with the petrosal is slight; the most marked portion of 

 the foramen lacerum posterius is just in front of the paroccipital. The forward extension 

 of bone is simply a flattened plate, nearly four-sided, but tapering a little, abutting by a 

 straight, transverse suture against the body of the sphenoid ; longitudinally ridged under- 

 neath, smooth and slightly concave above, with an oblique groove alongside each anterior 

 corner. 



The exoccipiials rise from the back part of the body, develop the superior two-thirds 

 of the condyles, and close over the foramen magnum, where, however, they do not ordina- 

 rily coalesce ; the line of separation remained in all the skulls examined. They form 

 a broad arch, whose longitudinal expansion is oblique, perforated on either side, at the 

 base of the paroccipitals, and notched in the middle of the upper border for a de- 

 scending process of the superoccipital ; sometimes the upper border has a well marked 

 prominence indicating the point where the superoccipital and mastoid come together. 



I have never found the paroccipitals distinct from the exoccipitals. They form pointed 

 conical processes of moderate length, directed downward, almost parallel with each other, 

 roughened for muscular attachment. Their bases abut against the petromastoids ; a deep 

 notch separates them from the condyles. 



The superoccipital is rarely, if ever, confluent with the exoccipitals. I have never 

 seen it thus united. On the other hand, its bony union with the parietals is fre- 

 quent, and with the "temporal bone," at the junction of the mastoid and squamo- 

 sal, is sometimes seen. The lambdoidal suture, when not obliterated, is very irregular 

 in direction, and mostly squamous in character, the outer surface of the superoccipital 

 being bevelled for some distance. The superoccipital is a triangular pyramid, with an 

 excavated base and sides : the concavity of the former being for the accommodation of 

 the brain, and of the latter for muscular attachments. The excavations of the sides are 

 virtually produced by the elevation of the occipital crest, which forms a segment of a 

 circle from side to side ; and by the beginning of the sagital crest, which runs directly 

 forward from, and at right angles with, the middle of the transverse crest. The thickness 

 and solidity of the bone, however, is not entirely owing to these crests. 



Confluence of the hasi-, pre-, ali- and orhito-sphenoid takes early place, and, when per- 

 fected, results in the single complex bone ordinarily called by the collective name "sphe- 

 noid." I find no traces of separation of these four bones in the youngest specimens 

 examined. As might be expected from its composite nature, the connections of the 

 bone are numerous. The contiguous bones are : — behind, the basisphenoid, and more 



