48 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 57 



and destroyed the remains of the radiating canal system appear as 

 fine, more or less irregular, shiny lines on the dark background. 



Alimentary canal. — The alimentary canal is an open spiral located 

 concentrically in the umbrella about midway between the center and 

 margin of the disk (pi. 9, fig. 5). It is clearly shown in over two 

 hundred specimens in the collection. The anterior or oral end opened 

 on the surface of the subumbrella at a point about one-half the 

 distance between the center and the outer margin, and the posterior 

 or anal end opened farther out toward the margin. The coil of the 

 canal was dextral or left to right and probably nearly on the same 

 plane except that the anterior end bent downward from the region 

 of the oesophagus and the anal end may also have been curved 

 slightly downward. The bending of the anterior side is indicated by 

 fig- 5. pl- 9> and text fig. 5. 



The canal appears to be more or less corrugated (pi. 9, fig. 3 ; and 

 pi. 10, fig. 3). Whether this corrugation has anything to do with 

 the radial canals or lobes of the umbrella has not been satisfactorily 

 •determined, except that the radial lobation and the divisions formed 

 by the slight constrictions causing the corrugation appear to be more 

 or less in accord in size and position. The corrugations show more 

 clearly on the outer margin of the canal. The canal is beautifully 

 outlined on the dark, smooth shale by the glistening silver-like luster 

 of the stomach section and the less prominent but distinct outlines 

 of the oral and intestinal sections. 



The canal is divided into four sections that, compared with the 

 typical holothurian alimentary canal, may be considered as the oral 

 chainber, oesophagus, stomach, and intestine. 



The oral chamber is indicated (fig. 5, pi. 9) at the inner end of the 

 spiral alimentary canal. The chamber extends from the outer end 

 to the constriction indicating the oesophagus a little beyond the dotted 

 line leading from the center out to the letters " cr ". This chamber 

 is also more or less clearly shown by fig. 3, pi. 8 ; fig. i, pi. 9 ; and text 

 fig. 5. (In this description it must be constantly recalled that we are 

 dealing with specimens flattened in the shale.) 



The outer opening of the oral chamber is best shown by fig. 5, pi. 

 9. A number of specimens show that from each side of the flattened 

 opening there is a short projecting arm which supports a cluster of 

 short tentacles, or, if we interpret the short arm as a strong tentacle, 

 with a disk to which are attached digits, the whole tentacle being 

 retractile and capable of being withdrawn into the oral chamber. 

 Some of the specimens suggest a three-lobed disk (text fig. 5). With 



