. On the anatomy of vertebrates [electronic resource] . o in Manatus, fig. 239, in which itslightly descends: in Halichore,1igs. 292, 294, 22, it is bent downmore abruptly: in Rhytina the angle of the upper contour of therostrum is greater than in Manatus, that of the lower contour lessthan in Halichore, exemplifying, as in other parts of the skeleton,an intermediate character. All the skull-bones are massive inSirenia, and, save in the in-stances of anchylosis, aresomewhat loosely connectedtogether. In the Dugong thebasioccipital, fig. 294, 1, is atriradiate bone, the two shortrays diverging
. On the anatomy of vertebrates [electronic resource] . o in Manatus, fig. 239, in which itslightly descends: in Halichore,1igs. 292, 294, 22, it is bent downmore abruptly: in Rhytina the angle of the upper contour of therostrum is greater than in Manatus, that of the lower contour lessthan in Halichore, exemplifying, as in other parts of the skeleton,an intermediate character. All the skull-bones are massive inSirenia, and, save in the in-stances of anchylosis, aresomewhat loosely connectedtogether. In the Dugong thebasioccipital, fig. 294, 1, is atriradiate bone, the two shortrays diverging posteriorly tojoin the exoccipitals, andforming the lower end of eachcondyle. The exoccipitals, 2,almost meet above the fora-men magnum: they have ashort rough paroccipital pro-cess. The superoccipital, 3,is early anchylosed to theparietals, which have equallycoalesced into a single sub-quadrate massive bone, , 7, with the sides bentdown at nearly a right anglewith the almost flat upperpart, which is perforated by aridge descends from the inner. Skull of Dugong (Iliilicliore indicus). foramen parietale. A falciformsurface. The basisphenoid, , 5, has coalesced with the alisphenoids, which are groovedboth behind and before, not perforated, by the trigeminal massive pterygoids are anchylosed to the base of the ali-sphenoids : the posterior ends of the palatines, which are wedgedinto the interspace between the ento- and ecto- pterygoid pro-cesses, send upward a part which appears in the temporalfossa behind the maxillary. The presphenoid, as a compressed6 rostrum, is wedged between the lamina? of the vomer, and hascoalesced with the confluent orbitosphenoids which it is no e sella turcica. The orbitosphenoids are perforated VOL. 11. xciv. p. F 434 ANATOMY OF VERTEBRATES.
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