404 Bashford Dean Memorial Volume 



posed between the cardiac stomach and the pylorus. It seems probable that, when 

 present, this di\asion in Chlamydoselachus is homologous with a part of the pyloric 

 stomach of Heptanchus. 



THE PYLORIC VESTIBULE 



In my specimen No. I the cardiac stomach narrows considerably near its caudal end. 

 It is marked off from the next division, which I shall call the pyloric vestibule, by a sharp 

 constriction. The pyloric vestibule is cylindrical in form and is of smaller caHber than 

 the cardiac stomach, though decidedly larger than the pylorus. The vestibule leads off 

 from the dorsal surface of the cardiac stomach, beginning about 10 mm . from its caudal 

 end, and extends somewhat cephalad, dorsal to the cardiac stomach, for a distance of 

 about 25 mm., then makes an abrupt turn dorsad and caudad before joining the pylorus 

 which extends obHquely to the right and caudad. Thus the pyloric vestibule, considered 

 together v,ith the adjoining portion of the cardiac stomach, is somewhat S-shaped. In 

 Text'figure 72 the pyloric vestibule (py.ves.) has been exposed by turning the cardiac 

 stomach to the left. Therefore the vestibule has been rotated through an angle of nearly 

 90° and appears almost as if viewed, in its natural position, from the right side. In the 

 specimen under consideration, the pyloric vestibule is about 35 mm. long and (in a col- 

 lapsed and flattened condition) about 22 mm. wide in its widest portion which is near its 

 junction with the cardiac stomach. Its wall is about 1.5 mm. thick and is of the same 

 general character as the wall of the cardiac stomach. The sharp constriction between 

 the cardiac stomach and the pyloric vestibule is more marked internally since here the 

 flattened lumen has a v,^dth of only 15 mm., which is 4 mm. less than the diameter of the 

 lumen of the adjoining portion of the pyloric vestibule. At its pyloric end, the vestibule 

 narrows abruptly to join the pylorus; here, the entrance has the same diameter as the 

 lumen of the pylorus. 



In specimen No. Ill, the pyloric vestibule is much smaller. It is situated on the 

 dorsal side of the caudal end of the cardiac stomach. In life it was probably spherical, 

 but it is now much flattened by pressure between the cardiac stomach and the dorsal 

 body wall; it has been hardened in that condition. Externally, on its anterior border 

 it is marked off from the cardiac stomach by a deep groove. Internally, its lumen is 

 partially separated from that of the cardiac stomach by a crescentic valve-like flap almost 

 completely encircling the residual lumen but leaving a circular aperture about 15 mm. in 

 diameter. On the anterior side, where it is best developed, the width of this flap is 

 about 5 mm. I am of the opinion that the flap, as such, is an artifact due to pressure, 

 since by stretching the wall of the stomach longitudinally the flap may be reduced to 

 a low fold. There remains, however, a very decided constriction marking off the pyloric 

 vestibule from the cardiac stomach. An aperture about 4 mm. in diameter leads off from 

 the anterodorsal side of the pyloric vestibule into the pylorus which extends obliquely 

 to the right and caudad. The proximal third of the pylorus adheres firmly to the wall 

 of the pyloric vestibule. 



