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PROCEEDINGS OF THE NATIONAL. MUSEUM 



VOL. 81 



directions — posteriad, mediad, laterad, ventrad, and dorsad. (Fig, 3, 

 C.) The spines are large, the largest ones (posterior) being 125^ 

 long and 32ju, broad at the base. They are rounded at the base and 

 bluntly pointed at the tip and only very slightly curved. When the 

 proboscides are retracted a row of much smaller spines can be seen 

 on the anterior margin of the body between the proboscis sacs and 

 the oral sucker. (Fig. 3, B.) There are five or six of them on 

 each side, similar in shape to those of the proboscides, but only about 



20/x in length. The anterior 

 portion of the body and the 

 more anterior portion of the 

 posterior part were seen in 

 the fresh specimens to be 

 covered with conspicuous 

 spines, but in the mounted 

 specimens most of the body 

 spines appear to be missing. 

 It seems likely that the cor- 

 rosive-acetic fluid in which 

 the worms were fixed had a 

 tendency to dissolve them. 



The oral sucker is on the 

 ventral side and triangular 

 in shape, measuring 150/x to 

 ISO^u in length and usually a 

 little less in width. The 

 ventral sucker is large and 

 powerful, measuring 360;u 

 to 425/i lengtliAvise and 288/a 

 to 345/i transversely. It is 

 situated at about the junc- 

 tion of anterior and poste- 

 rior portions of the body, though its center is usually a little anterior 

 to that level. The prepharynx is 75jw to 90/a in length, followed by 

 a well-developed pharynx about equal in size to the oral sucker (150ju, 

 to 185/i long by 122ja to 145ju, wide). The intestine forks very shortly 

 behind the pharynx, but this region of the intestine is frequently en- 

 larged so that the posterior margin of the fork may be as much as 

 250|U behind the pharynx. The ceca could not be followed after they 

 reach the vitellaria. 



The cirrus pouch is very large. It opens in a genital pore situated 

 in the fork of the intestine anterior to the ventral sucker, has one 

 to three twists or loops in this region, then passes on either the right 

 or left side of the ventral sucker, and ends in a gradually enlarging 



0.7. miri. 



I mm. 



Figure 3. — A, Rhopalias macracanthus, new spe- 

 cies ; B, R. macracanthus, anterior end with 

 proboscides retracted ; C, anterior end with 

 proboscides exserted 



