326 



THE ELASMOBRANCH FISHES 



Mandibular canal, 275; nerves to, 243 

 Mandibular groove, 262; nerve to, 224 

 Mandibular somite, 99 ; muscle derivatives 



of, 99 

 Marginal cartilage of clasper, 81-82 

 Maxillaris branch (V), 223, 240, 241; 



ganglion of, 240, 241; origin of, 241 

 Meckel's cartilage. See Mandible 

 Median anterior sulcus, 231 

 Median cardiac vein, 215 

 Median cerebral artery, 165, 183 

 Median hypobranchial artery, 163, 178, 



179 

 Median hypobranchial piece, 46, 65, 67 

 Median longitudinal bundles of medulla, 



235 

 Median olfactory nucleus, 221, 232, 239 

 Median pterygial artery, 191 

 Median pterygial vein, 213 

 Median vesicle, 296, 298; derivation of, 



298, 300; relation of, to segmental duct, 



296, 298; relation of, to collecting tu- 

 bules, 297 

 Medulla, 222, 235, 236; finer structure of, 



236; section through, 236 

 Melanophore, 26; in Heierodonlut^, 26 

 Meningeal lining, 237 

 Mesencephalon, 221, 222, 230, 234; fibers 



terminating in, 239 ; in Heptanchus, 



221—222 

 Mesenteric arteries: inferior, 167—168, 



190-191 ; superior, 167, 188-190 

 Mesenteries, 121, 127-128; in Heptanchits, 



121; in Hypnos, 127 

 Mesopterygium, 50, 77, 78 

 Mesorchium, 290; vasa efferentia on, 302 

 Mosorectum, 121, 297; nephrostomes on, 



290 

 Mesovarium, 290, 303 

 Metapterygium, 50, 77; development of, 



77-79 

 Metencephalon, 221, 222, 230, 234; cavity 



of, 235-236; in Heptanchus, 221-222 

 Midbrain. See Mesencephalon 

 Mixed nerve, 243, 246 

 Motor fibers, 236; origin of, 236 

 Motor (ventral) root, 246 

 Mouth, 5, 121, 128 

 Mucous pores, 7, 262 

 Multipolar nerve cell, 229 

 Muscle buds, 109, 110; growth of, 238; 



of fin, 109, 110; bearing of, on origin 



of fin, 110 

 Muscles of eye. See Musculature 



Muscle fibers, 96-97; in CladoselacJius, 1; 

 metamorphosis of, to electric discs, 114— 

 115 



Muscularis, 170 



Musculature: buccal and pharyngeal, 90- 

 93, 101-108; dorsal bundles, 89; of 

 claspers, 95, 110-112 ; of Elasmobranchs 

 in general, 96-112; of electric organ 

 (developing), 112-114; of eye, 89-90, 

 99-100; of eyelid, 102-103; of fin, 89, 

 95, 109-110; of Heptanchus, 89-95; of 

 hypobranchial region, 93, 108-109 ; to 

 lens, 269-270; ventral bundles, 89, 97 



Musculospinal artery, 192 



Mustelus californicus, 9 ; color of, 26 ; nic- 

 titating membrane of, 102 



Myeleneephalon, 221, 222, 235; cavity of, 

 235-236; in Heptanchus, 221; nerves 

 from, 235 



Myelonal artery, 186, 192 



Myelonal veins, 208 



Myliohatis californicus, 3, fig. 8 



Myoblast, 96 



Myocoele, 96 



Myosepta, 89, 96, 97; direction of, 89, 96, 

 97; in electric organ, 112 



Myotome, 96, 109; derivative of, 109 



Nasal apertures, 5; in Elasmobranchs in 

 general, 264-265; in Heptanchus, 5, 44, 

 258 



Nasal capsule. See Olfactory capsule 



Nasal cartilage, 43-44, 58 



Nasal pit or cup, 5; relation of, to oro- 

 nasal groove, 122 



Neopterygium, 79 



Nephrostome, 296, 297, 298, 301; develop- 

 ment of, 298 



Nerve cells, 229 



Nerve fiber. See Axone 



Nerves: cranial, 223-227, 238-246; occip- 

 itospinales, 227, 245-246; spinal, 227- 

 228, 246-247; sympathetic, 247-248 



Nervous collector, 228, 247; relation of, 

 to origin of paired fins, 247 



Nervous system: central, 221-228, 229- 

 248; development of, 230; in Elasmo- 

 branchs in general, 229-248; in Hep- 

 tanchus, 221-228; peripheral, 222, 238 



Neural arches, 47, 69; composition of, 47- 

 48 



Neural canal, lining of, 237 



Neural crest, 238 



Neural fold, 230 



