The Anatomy of Chlamydoselachus 477 



devoted much attention to the innervation of the lateral line system, renaming most of 

 the divisions of that system in accordance with their nerve supply — a method first 

 employed by Cole (1896) in his work on Chimaera, and which has since been generally 

 adopted. 



The reader who is not familiar with the terms employed in the classification, on 

 a functional basis, of the cranial nerve components of fishes should consult Herrick, 

 1899, pp. 7-19; Johnston, 1905.1, pp. 176-184 and PI. IV; Norris and Hughes, 1920, 

 Fig. 51, showing the cranial nerve components of Squalus in color; and Goodrich, 1930, 

 pp. 725-755. 



A complete resume of the rather lengthy descriptions, by Hawkes (1906) and Allis 

 (1923), of the cranial nerves of Chlamydoselachus seems unnecessary since, for the most 

 part, these nerves are much like those of other elasmobranchs (e.g., Heptanchus, briefly 

 described by Daniel, 1934; and Squalus, elaborately described by Norris and Hughes, 

 1920). It seems sufficient to mention some respects in which the cranial nerves of Chlamy^ 

 doselachus dxz more or less unique, or in which the descriptions of authors differ. The 

 following account is based primarily on Hawkes' description. 



A nervus terminalis is not mentioned by Garman, nor is it shown in any of his 

 figures of the brain. It is, however, described by Hawkes (who calls it Locy's nerve, 

 L.?v[., Figure 13, plate IV) as large and welhdefined. Originating near the median Hne, 

 somewhat to the ventral side of the forebrain, it passes outward, curving upward along 

 the anterior and upper side of the olfactory stalk to be distributed between the end of the 

 stalk and the beginning of the olfactory capsule. On reaching this point, the nerve 

 becomes somewhat enlarged by flattening, then breaks up into a number of fine branches 

 which pass toward the olfactory epithelium but could not be traced to their endings. 



Allis (1923) writes that in his specimen a small nervus terminalis runs outward 

 along the anterior surface of each tractus olfactorius, and then turns upward onto its 

 dorsal surface, as stated by Hawkes. The terminal portion of the nerve of the left side 

 is shown (without a label) in Figure 7, plate III. 



The olfactory nerve of Chlamydoselachus is neither figured nor mentioned by any 

 author. From this we may surmise that it is essentially the same as in other elasmobranchs, 

 developing from neuroblasts in the epithelium of the olfactory capsule and extending as 

 a double nerve backward to the olfactory bulb. In Heptanchus, as in some other forms, 

 the nerve is so short as to be hardly recognisable without microscopical examination. 



The optic nerve (2, Figures 25, 26 and 27, plate VI, after Garman) does not take 

 the most direct route to reach the eyeball. As described by Allis (1923) and as shown in 

 his Figs. 52 and 59 (the latter reproduced as my Figure 7, plate III) this nerve runs antero- 

 laterally. Having issued through its foramen, it turns ventro-latero-posteriorly around 

 the anterior end of the capsular sheath that encloses the orbital process of the palato- 

 quadrate, and reaches the eyeball, passing ventral to the somewhat Hgamentous portion 

 of the connective tissue that attaches the capsular sheath to the anterior wall of the orbit. 



