402 Bashford Dean Memorial Volume 



the pyloric vestibule and the pylorus into view, and the rectal gland has been turned to 

 the left. In this paper, the terms right and left mean the right and left sides of the fish 

 itself, regardless of its position with respect to the observer. 



THE PHARYNX 



The mouth, including the teeth, has been adequately described by Gudger and Smith 

 (1933). The pharynx is of importance for respiration, but since it affords passage for 

 food it must be briefly considered from this point of view. 



The mouth and pharynx of Chlamydoselachus form one large cavity, the oro- 

 pharyngeal cavity. For so slender a shark, the size of this cavity when fully distended 

 is remarkable (Text-figure 2, p. 337)- Although a large mouth does not necessarily 

 imply that large objects are taken as food, in the case of Chlamydoselachus there is col- 

 lateral evidence, such as the character of the teeth, indicating that the animal seizes and 

 swallows Hving prey of considerable size. It seems Hkely that the elaborate pharyngeal 

 musculature, already considered, assists in the act of swallowing the prey, snake-fashion. 



Almost the entire oropharyngeal cavity is lined with close-set denticles. On the 

 lining of the roof, the denticles are exceedingly small. On the floor, especially where 

 this is upraised to form a structure superficially resembUng a rudimentary tongue, the 

 denticles are appreciably larger. Some of these denticles, in a region overlying the thy- 

 roid gland, are shown in Text-figures 75 and 76, p. 417- On the inner surfaces of the 

 gill-arches, excepting only the hyoid arch and the dorsal portions of the most posterior 

 branchial arch, they are particularly large, but are still smaller than those at the angles 

 of the mouth (Text-figure 10, p. 345), described and figured by Gudger and Smith (1933). 

 The larger denticles are of the same general character as those of the epidermis ; but the 

 central cusp is longer and sharper, and curves backward. The denticles of the gill-arches 

 and the floor of the pharynx offer little resistance to a finger tip passed over them in 

 a cephalocaudad direction, but pierce the epidermis and cling tenaciously when the 

 finger tip is pulled over them in the opposite direction. Presumably, the pharyngeal 

 denticles assist the animal in retaining its hold on slippery prey, partly swallowed. 

 Garman (1885.2) shows denticles on the inner surfaces of the gill-arches of his specimen 

 (my Text-figure 77, p- 421), but they appear larger than those found in a corresponding 

 situation in my specimens. 



ESOPHAGUS AND CARDIAC STOMACH 



As in most elasmobranchs, the wide, distensible esophagus passes without abrupt 

 demarcation into the large, thin-walled cardiac portion of the stomach. In Chlamydo' 

 selachus one cannot tell precisely where the esophagus leaves off and the stomach begins. 

 The combined length of esophagus and cardiac stomach is remarkable (Text-figure 72; 

 and Table I, p. 412), since together they form about half the total length of the digestive 

 tube. In my best-preserved specimen, No. I, the collapsed and flattened esophagus is 



