. Chordate morphology. Morphology (Animals); Chordata. hyoid arch line mandibular arch line nasal openmg Figure 13-28. Three stages in the development of the sensory-line system of Squo/us acanthios. (After Holmgren and Pehrson, 1949) end of the supraorbital line of the shark. The infraorbital is then peculiar because of its relationship to the olfactory capsule and also its forking (only in Hydrolagus); both parts connect across the midline, and the upper also connects along the midline with the supraorbital connective. The modifications of these lines may be related to the jaw changes and th
. Chordate morphology. Morphology (Animals); Chordata. hyoid arch line mandibular arch line nasal openmg Figure 13-28. Three stages in the development of the sensory-line system of Squo/us acanthios. (After Holmgren and Pehrson, 1949) end of the supraorbital line of the shark. The infraorbital is then peculiar because of its relationship to the olfactory capsule and also its forking (only in Hydrolagus); both parts connect across the midline, and the upper also connects along the midline with the supraorbital connective. The modifications of these lines may be related to the jaw changes and the development of the snout. The chimae- rid differs from the shark in terms of the position of its nasal capsule much as the dipnoan differs from the other choa- nates. Fossil gnaihostome fishes In the arthrodires and acantho- dians, the same general canal pattern is seen. In the acan- thodian the canals lie in the scales covering the head. In one genus, Poracanthodes, there is a reticular canal system embedded in the scales. There are distinct mandibular and hyoid arch lines which join at the angle of the mouth, and there is a pit line of the cheek which joins the jugal section with the preopercular section. The preopercular section lies far forward of the spiracle and does not connect with the temporal line. The position of this line indicates that these. nasal opening Figure 13-29. Sensory-line grooves on the head of Hydrolagus. A, lateral view; B, interconnec- tions on snout. 414 • THE NERVOUS SYSTEM. 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 not perfectly resemble the original Jollie, Malcolm. New York, Reinhold
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