. Outlines of zoology. tilaginous (eventually bony) centra, outside the sheath of the noto-<; This is called an arcicentrous vertebral column. The skull is a cartilaginous case, with a spacious cavityfor the brain, a large posterior aperture or foramen magnumthrough which the spinal cord passes, two condyles working•on the end of the vertebral plate, a large ear capsule oneach side posteriorly, a similar nasal capsule on each sideanteriorly, a long rostrum in front, two fontanelles on theroof. Compared with the skull of a cod or of a higherVertebrate, that of a skate is simple; it is
. Outlines of zoology. tilaginous (eventually bony) centra, outside the sheath of the noto-<; This is called an arcicentrous vertebral column. The skull is a cartilaginous case, with a spacious cavityfor the brain, a large posterior aperture or foramen magnumthrough which the spinal cord passes, two condyles working•on the end of the vertebral plate, a large ear capsule oneach side posteriorly, a similar nasal capsule on each sideanteriorly, a long rostrum in front, two fontanelles on theroof. Compared with the skull of a cod or of a higherVertebrate, that of a skate is simple; it is not ossified, nor?divided into distinct regions, nor has it anything corre-sponding to the investing membrane bones, which in higheranimals are added to the original foundations of the skull,nor do the visceral arches in the skate take part in formingthe skull, which arises, as usual, from parachordals, trab-?eculse, sense capsules, etc. 534 PISCES FISHES. The visceral arches are primitively supports for the a, a. Fig. 280.—Under surface of skull and arches ofskate.—After W. K. Parker. /.I, First labial cartilage; /?., rostrum;^., trabecularregion; n,c., nasal capsule; ^ antorbital cartilage; palato-pterygo-quadrate; Meckels car-tilage; hyo-mandibular ; , hypobran-chials ; , fifth ceratobranchial; cerato-hyal;/.2-4, labial cartilages. wall of the anterior part of the food canal, but the first twoof them are much modified in connection with the jaws. THE SKELETON. 535 The upper jaw of the skate is a strong transverse bar,,formed from the union of two palato-pterygo-quadratecartilages. The lower jaw is a similar bar formed from theunion of two Meckels cartilages. From the ear capsule to the articulation of upper andlower jaw there extends on each side a club-shaped cartilage,which connects the jaws with the skull, known as the hyo-mandibular or suspensorium. It is the upper half of thesecond arch. Attached to it is a slender fou
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
