272 



EDWARD S. MORSE. 



A view of the posterior end of the animal reveals a single long 

 siphonal opening which often changes its outline, at times being 

 an oblong, oval slit, but usually the upper part, corresponding 

 to the anal opening, is much larger, giving the aperture a double- 

 gourd-shaped form, the upper bulb being larger. Above the 

 anal region, just where the two shells meet, is an unpaired tubercle, 

 or tentacle which is contractile. Stempell figures a similar 



FIG. 13. Termination of branchia. 



Q -\^-wr- C 



FIG. 14. Siphonal opening: .4, B, from above; C, D, from behind; E, from behind 



at an angle. 



tubercle in 5. togata, and in another form to be described later a 

 very long tentacle is seen. Just below this tentacle a pair of 

 blunt tubercles arise which are very contractile and appear at 

 times as two and even three pairs of tubercles. The sides of 

 the anal opening are without tubercles. The narrow branchial 

 opening is bordered on each side by from six to eight short 

 tubercles or papillae hardly varying in size. These are also 

 contractile. A few attitudes of the siphonal opening are shown 

 in Fig. 14. 



A view of the siphonal opening from the side shows no pro- 

 trusion as in the siphonal expansion of siphonated lamelli- 

 branchs. Indeed there is no appearance of a siphon, simply an 



