. Outlines of zoology. Zoology. 484 PISCES—FISHES. process projects outwards, and bears a minute hint of a rib. From the dorsal surface of each centrum two neural processes arise, and arch upwards for a short distance on each side of the spinal cord. Between each two vertebral there is at each side a broad intemeural plate, which not only fills what would be a gap between the neural processes _ft__iBi____ ^„^ and the slightly de- • i!,i'l"'\ veloped neural spine, but also links the vertebrae together, so that on surface view the segmentation of the vertebral column is far from obvious. In
. Outlines of zoology. Zoology. 484 PISCES—FISHES. process projects outwards, and bears a minute hint of a rib. From the dorsal surface of each centrum two neural processes arise, and arch upwards for a short distance on each side of the spinal cord. Between each two vertebral there is at each side a broad intemeural plate, which not only fills what would be a gap between the neural processes _ft__iBi____ ^„^ and the slightly de- • i!,i'l"'\ veloped neural spine, but also links the vertebrae together, so that on surface view the segmentation of the vertebral column is far from obvious. In the caudal verte- brae, what seem to be the transverse pro- cesses are directed downwards, to form a haemal arch enclos- ing the caudal artery and vein. In the lozenge-shaped spaces between the vertebras lie gelatin- ous remains of the notochord. The vertebral column de- velops, as usual, from the mesodermic sheath of the endo- dermic notochord. The skull is a car- tilaginous case, with a spacious cavity for the brain, a large posterior aperture or foramen magnum through which the spinal cord passes, two condyles working on the end of the vertebral plate, a large ear capsule on each side posteriorly, a similar nasal capsule on each side anteriorly, a long rostrum in front, two fontanelles on the roof. Compared with the skull of a cod or of a higher Vertebrate, that of a skate is simple ; it is not ossified, nor. Fig. 203.—Under surface of skull and arches of skate'.—After W. K. Parker. l.\ First labial cartilage ; R., rostrum; r>., tra- becular region ; , nasal capsule ; , antor- bital cartilage ; palato-pterygo-quadrate ; Meckel's cartilage; , hyo-mandibular; , hypobranchials ; , fifth cerato- branchial; , cerato-hyal; , labial cartil- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
