ABT. 7 



A NEW RHIZOCEPHALAIT PARASITE BOSCHMA 



at the extreme right of the figure. It is surrounded by a thick 

 sphincter, as a result of which the parts around the mantle opening 

 slightly protrude, forming thereby a kind 



of wall. The shape of the mantle open- ^'^S-'^^^^vS^^ 



ing is more distinctly visible in Figure 2, '''^y-^^-'--^'^'--'"'- 



which represents a part of the anterior *^v;- . . '%\ 



region of the animal. 'il| 



For the study of the internal structure 

 the mantle has been removed from the 

 visceral mass. Figure 3 shows the greater 

 part of the internal surface of the mantle. 

 At the left side of the figure the mantle 

 opening, surrounded by its strongly devel- 

 oped sphincter, may be seen. Slightly 

 above the center of the figure the region 

 of the stalk is to be seen as a concavity 

 in a part of the mesentery. The latter, 

 which has been detached from the visceral 

 mass, extends from the sphincter of the 

 mantle opening to the posterior part of 

 the dorsal surface (behind the stalk). Only a part of the mesentery, 

 the posterior part, is found exactly at the dorsal surface; the anterior 



Figure 2.— Briarosaccus callosus, 

 part of the mantle, with the man- 

 TLE OPENING. APPROXIMATEty 

 NATURAL SIZE 







.tijS^' 



Figure 3.— Briarosaccus callosus, the greater part of the mantle, internal surface 



part of the mesentery stretches from the mantle opening along the 

 right surface of the mantle toward the stalk. The mantle opening 



