The Anatomy of Chlamydoselachus 



489 



THE SENSORY CANAL SYSTEM 



The distribution of the sensory canals of Chlamydoselachus has been described by 

 Garman (1888), Hawkes (1906) and AUis (1923 and 1934). Their descriptions have been 

 briefly reviewed by Gudger and Smith (1933), who added some observations on the 

 specimens in the American Museum of 

 Natural History. This account, which is 

 fairly well illustrated, need not be repeated 

 here. Some of the sensory canals of the 

 head are shown in my Text'figure 70, 

 page 396; and in Text'figure 124. The 

 innervation of the sensory canals of the 

 head has been worked out by Hawkes 

 (1906), whose drawing is reproduced as 

 my Figure 29, plate VII. For comparison, 

 I have inserted a similar figure (Text-figure 

 125) representing the sensory canals of 

 the head in Squalus. It remains to con- 

 sider the sensory canal system of Chlamy^ 

 doselachus briefly from a comparative 

 point of view. 



In all adult elasmobranchs, the sen- 

 sory canals are fairly similar in their dis- 

 tribution. A pair of these canals extend 

 in or under the skin, from the tip of the 

 tail to the vicinity of the ear, where they 

 connect with other canals branching over 

 the various regions of the head. At inter- 

 vals, the canals open to the exterior by 

 means of pores, so that their approximate 

 distribution can usually be traced without 

 dissection. 



Among living elasmobranchs it is 

 very unusual for the sensory canals to be 

 present as open grooves through so great 



_ i iamp 



Text-figure 124. 

 Dorsal view of the head of Chlamydoselachus, show- 

 ing the external openings of the ampullae of Lorenzini 

 and of the laterosensory canals. 



amp, ampuUary pores; end, pore of the endolymphatic duct; iop, 



infraorbital laterosensory pores; lie, lateral line canal of body; 



sop, supraorbital laterosensory pores; sp, spiracular laterosensory 



canal; spr, spiracle. 



Redrawn after Allis, 1923, Pi. 11. 



a portion of their extent as is the case in 

 Chlamydoselachus. The lateral line of Chlamydoselachus is an open groove from the tip of 

 the tail almost as far forward as the spiracle (Garman, 1888). The anterior portion of the 

 lateral line (lie.) is shown in Text-figure 124. Several of the longest sensory canals of the 

 head are open — in particular, the spiracular (sp. in Text-figure 124), the gular and the oral. 

 The latter are shown in Gudger and Smith's (1933) Figure 7, plate II, after AUis; they 

 appear, without labels, in my Text-figure 70, page 396. In Figure 29, plate VII, after 



