. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. The Anatomy of Chlamydoselachus 485 dency toward unification of the system. The trigemino'facial complex is less primitive than that of Chimaera, but more so than that of most elasmobranchs. Hawkes' general conclusion is that the cranial nerves of Chlamydoselachus are not in so primitive a con' dition as would be expected from the low position of the species in the taxonomic series, especially as regards the vagus and the lateralis nerves. THE SPINAL NERVES Hawkes' description (1906, pp. 985-987) of the spinal nerves of Chl
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. The Anatomy of Chlamydoselachus 485 dency toward unification of the system. The trigemino'facial complex is less primitive than that of Chimaera, but more so than that of most elasmobranchs. Hawkes' general conclusion is that the cranial nerves of Chlamydoselachus are not in so primitive a con' dition as would be expected from the low position of the species in the taxonomic series, especially as regards the vagus and the lateralis nerves. THE SPINAL NERVES Hawkes' description (1906, pp. 985-987) of the spinal nerves of Chlamydoselachus is concerned mainly with the spinal nerve roots. I quote her account almost entire: The ventral root of the first true or complete spinal nerve originates between the first and second vertebrae. Spinal nerves 1, 2, 3, 4, 5 (Fig. 1, pi. LXVIII) [my Figure 29, plate VII] unite with the spino'occipital nerves into a strand, which passes backwards, then out' Text-figure 121. Diagram of spinal nerves from anterior, middle and tail regions of Chlamydoselachus. , connecting strands between dorsal and ventral roots; , dorsal branch; , dorsal root with its ganglion; 'Ho., notochord; ^., spinal nerve; , ventral branch; V. C, vertebral column; V. R., ventral root. After Hawkes, 1906, Text-fig. wards towards the pectoral girdle. Spinal nerves 6 and 7 unite with one another before joining this plexus. Spinal nerve 8 runs by its side, but does not actually join. The spinal plexus gives off anteriorly two branches ( and ). Branch , which is connected with vagus 6, passes forwards and downwards to join branch The resulting compound nerve passes forward near the median ventral line to supply a portion of the median man- dibular or hypoglossal musculature. It is probable that this nerve consists only of fibers from the spino-occipital nerves, and would therefore be the homologue of the hypoglossal nerve of higher forms. The brachial
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