The Anatomy of Chlamydoselachus 487 



collector is much more complex in Chlamydoselachus than it is in Heptanchus. In other 

 forms few nerves take part (as in Spinax), or the collector may be absent (as in Squatina 

 and in Raja). 



The nervus collector has been studied minutely by Braus and others (cited by 

 Osburn, 1906 and 1907) because of its possible relation to the origin of the paired fins, 

 with results that have been interpreted differently by exponents of the gill-arch and 

 fin'fold theories respectively. 



From a functional point of view, the nervus collector is somewhat comparable to 

 the caudal longitudinal collecting nerve trunks described by Speidel (1923) in Squalus 

 acanthias and in Raja laevis. In both cases, the longitudinal trunks and accompanying 

 nervous network provide a conducting system which may be effective in the coordi' 

 nation of muscular action. 



The innervation of the tropeic folds, described by Braus (1898), has been considered 

 in the section on the muscular system and is illustrated by my Text-figure 59, p. 386. 



THE SENSE ORGANS 



This account of the sense organs of Chlamydoselachus is necessarily very incomplete. 

 None of these organs has been described histologically, and my material is unfit for 

 study in serial sections. 



The external openings of the olfactory sacs have been described by Gudger and 

 Smith (1933), whose account is based on the descriptions of various authors, supple- 

 mented by their own observations ; but the internal structure of the olfactory organs of 

 Chlamydoselachus has never been described. 



The external appearance of the eye and the peculiar mechanism by which the 

 cornea may be protected in the absence of lids have been described by Gudger and Smith 

 (1933). In the present paper I have described the muscles of the eye and their innervation, 

 in the sections on the muscular system and the nervous system respectively. The internal 

 structure of the eye has never been described. 



Of the various sense organs of Chlamydoselachus, the lateral line or sensory canal 

 system and associated organs have received the most attention, but even here the various 

 authors (Garman, 1888; Hawkes, 1906; and Allis, 1923) are concerned only with gross 

 structure and distribution. The ear (membranous labyrinth) has been studied and describ- 

 ed by Goodey (1910.1). 



THE MEMBRANOUS LABYRINTH 



Goodey's (1910.1) Figs. 7 and 8, pi. XLIII, illustrating medial and lateral views of 

 the membranous labyrinth of Chlamydoselachus, are reproduced as my Figures 30 and 31, 

 Plate VII. His description (pp. 551 and 552) of this organ is best given in his own words : 



On removing the skin from the dorsal surface of the cranium it is seen that the parietal 

 fossa is rather deep and possesses four apertures, two on either side of the median longitudinal 

 line. One of these apertures, the anterior, is small, and transmits the ductus endolymphaticus. 



