. The elasmobranch fishes. Chondrichthyes. THE ELASMOBRANCH FISHES 277 and at tlie tip of the nose passes through to the ventral side. It then continues backward to meet the infraorbital (ioc). This condition is unlike that in Hep- tanchus (fig-. 228) in which the terminal part going to the infraorbital is usuall}^ broken in its course. The infraorbital drops back of the eye to a ventral position and then forward under the eye; after passing the ventral terminus of the supraorbital, it turns inward toward the middle line, where it approxi- mates or meets (Lae- margus) the infraor- bital of the
. The elasmobranch fishes. Chondrichthyes. THE ELASMOBRANCH FISHES 277 and at tlie tip of the nose passes through to the ventral side. It then continues backward to meet the infraorbital (ioc). This condition is unlike that in Hep- tanchus (fig-. 228) in which the terminal part going to the infraorbital is usuall}^ broken in its course. The infraorbital drops back of the eye to a ventral position and then forward under the eye; after passing the ventral terminus of the supraorbital, it turns inward toward the middle line, where it approxi- mates or meets (Lae- margus) the infraor- bital of the opposite side. It then continues forward and slightly outward to the tip of the nose. The hyonian- dibular canal {hmc.) in the sharks branches oi¥ posteriorly from the infraorbital at the place where the latter reaches a ventral posi- tion back of the eye. Essentially the same plan obtains in Squa- lussucMii (fig. 241) as that here described for Laemargiis. This plan is consid- erably modified in the rays. In these, the su- praorbital canal (soc, fig. 242) in its ventral course is characterized by a peculiar loop for- ward and outward. It then meets the infra- orbital ventrally as in sharks. The hyoman- dibular() in the rays is greatly modified. It passes from the infraorbital backward, outward, and then for- w^ard on the ventral side of the pectoral fin, making a large ventral loop (in- complete in Torpedo). It then perforates the fin at the side of the olfactory capsule, and continues its course on the dorsal side of the fin, first inward and backward; then it swerves far outward and backward and then inward to join an anterior scapular l)ranch (sc.^) from the lateral canal, forming with the scapular branch dorsally on the pectoral fin a characteristic Fig. 243. Cephalic cauals in Dicerobatis, dorsal view. (From Garman.) , commissural or supratemporal canal; hmc, hyoman- dibular canal; ioc, infraorbital canal; II., lateral line; soc, supraorbital can
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