The Anatomy of Chlamydoselachus 405 



In specimen No. II there is nothing resembUng a pyloric vestibule; the pylorus 

 comes off abruptly from the caudal end of the cardiac stomach and leads directly backward. 

 The aperture leading from the cardiac stomach to the pylorus is very small, but admits 

 a probe without difficulty. The muscular wall surrounding this aperture is unusually 

 thick; evidently it serves as a sphincter. In the specimen figured by Hawkes (1907) 

 and reproduced as my Text'figure 73, there is no division of the stomach corresponding 

 to what I have called the pyloric vestibule. I cannot reconcile this difference further 

 than to say that here, as in many other structures, Chlamydoselachus shows remarkable 

 variability. 



THE PYLORUS 



In all my specimens, the pylorus is a slender portion of the digestive tube which, 

 from superficial appearances, might more appropriately be designated a part of the small 

 intestine. However, the region under consideration undoubtedly corresponds to what 

 is called pylorus in other sharks, as in Galeus (Daniel, 1934, Fig. 135, p. 136). In Chlamy^ 

 doselachus (Text'figure 72) the caudal extremity of the pylorus (py.) projects into the 

 next division of the digestive tube, the bursa entiana (b.e.), as a large conical papilla, the 

 pyloric valve. The muscular layers of the pylorus appear to be continuous with similar 

 layers in the valve. At the summit of the papilla there is an aperture which, in the hard- 

 ened condition of the material, is still large enough to admit a probe easily. This opening 

 is the passageway from the pylorus to the bursa entiana. The cone-shaped valve is 

 asymmetrically placed and adheres, more or less, to one side of the bursa. 



On account of the overlapping of the pylorus by the bursa, in recording their lengths 

 for the purposes of Table I it was necessary to divide the region of overlapping equally 

 between them. In specimen No. I (Text-figure 72) the overlapping occurs mainly on 

 one side and is about 6 mm. in its greatest extent; the total length of the pylorus, including 

 its valve, is 36 mm. The width of the pylorus, in its present collapsed and flattened 

 condition, is about 8 mm. In specimen No. II the lumen of the bursa entiana overlaps 

 the pyloric valve for a distance of 14 mm. on one side and 6 mm. on the other. The total 

 length of the pylorus, including its valve, is 40 mm. In this specimen the pylorus is 

 cylindrical and its diameter is only 6 mm. In specimen No. Ill the pylorus is unusually 

 short. Its valve is overlapped, on one side only, by the lumen of the bursa entiana for 

 a distance of 6 mm. and its total length is 28 mm. At its widest point, which is near 

 its middle, the collapsed and flattened pylorus of this specimen measures 12 mm. across. 

 In specimens I and III the wall of the pylorus is a scant millimeter in thickness; in No. II 

 it is about 2 mm. thick. In all my specimens the inner surface of the pylorus is traversed 

 by longitudinal folds. These are more prominent in No. II because of the contracted 

 condition of the pylorus in this specimen. 



Hawkes (1907) describes the division which I have called the pylorus, as follows:' 

 "The shorter arm of the stomach (S. 1) differs from the larger anatomically and functionally. 

 It is a short, thick-walled tube incapable of distension, the lining mucosa of which is 



