. The elasmobranch fishes . Fig. 241. Sensory canals and ampullae of Lorenzini, Squalus suclclii. (Olive Swezy, orig.) A. Dorsal view. B. Ventral view. CO., commissural or supratemporal canal; , endolymphatic duct; hmc, hyomandibular canal; iba., inner buccal ampullae; ioc, infraorbital canal; isa., infraspiraeular (hyoid) ampuhae; II., lateral line; vie, mandibular canal; mpo., mandibular ampullae; , nasal aperture; oba., outer buccal ampullae; soa., supraophthalmic ampullae; soc, supraorbital canal; sp., spiracle. of ectoderm continuous with, and like that of, the placode for the ea
. The elasmobranch fishes . Fig. 241. Sensory canals and ampullae of Lorenzini, Squalus suclclii. (Olive Swezy, orig.) A. Dorsal view. B. Ventral view. CO., commissural or supratemporal canal; , endolymphatic duct; hmc, hyomandibular canal; iba., inner buccal ampullae; ioc, infraorbital canal; isa., infraspiraeular (hyoid) ampuhae; II., lateral line; vie, mandibular canal; mpo., mandibular ampullae; , nasal aperture; oba., outer buccal ampullae; soa., supraophthalmic ampullae; soc, supraorbital canal; sp., spiracle. of ectoderm continuous with, and like that of, the placode for the ear, but this extends both forward and backward. Forward it gives rise to the long canals of the head region. Backward it becomes the lateral line organ. Either way, in order to become a canal rather than an open groove the sensory cord or plate of ectoderm, usually as a pocket, pushes deep into the underlying corium. It may be mentioned here that at regular intervals throughout its course the sensory cord differentiates into patches of ectoderm, the end organs or neuro- masts characteristic of these canals. In the adult Elasmobranch the lateral line canals (figs. 240-242) are simi- lar in distribution. They extend in or under the skin from the tip of the tail to the segment of the ear. The lateral line canal in Chlamydoselachns is an
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