848 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [1 30] 



In the following, No. 1 was a living specimen somewhat flattened 

 under the compressor ; Nos. 2 and 3 alcoholic. Nos. 1 and 3 are doubt- 

 less the same individual. 



In No. 1 the last 17 segments show the reproductive organs. 



From a specimen collected July, 1885, the following measurements 

 were obtained: length of head, 3 mm , breadth, 2 mm ; length of neck, 

 6 mm ; breadth, 1.3 ram ; length of contractile bulbs, l rai ", breadth, 0-5 mm ; 

 length of posterior segment, 4 mra , breadth, 2.5 mm . 



Some dimensions of proboscides and hooks are: diameter at base, ex- 

 cluding hooks, 0.097 mm ; including hooks, O.l inm ; median diameter, ex- 

 cluding hooks, O.OC6 mm ; including hooks, 0.102 mm ; length of hooks on 

 base of proboscis, 0.02 to 0.03 mm ; breadth, 0.004 mm j length of median 

 hooks, 0.04 mm , breadth, 0.007 mm . 



The tumid base of each proboscis is prominently shouldered on the 

 outer side. In this respect it resembles R. tvageneri. There is, how- 

 ever, no single large hook as in that species, and besides there is a very 

 great difference between R. icageneri and R. longicorne in respect to the 

 conformation and arrangement of the hooks. 



Behind the basal enlargement the hooks are nearly straight, ap- 

 pressed closely to the surface of the proboscis, slender, sharp-pointed, 

 and, many of them, with a single short lateral basal prolongation. The 

 spirals are about 0.01 nmi apart, while the longest hooks are over 0.03 1111 " in 

 length. The points of the hooks in one spiral therefore cover the bases of 

 the preceding series. The hooks on the outer side of this part of the pro- 

 boscis are larger than those on the inner side. On the anterior part of the 

 basal enlargement of the proboscis they are smaller and crowded together 

 closely. The spirals are here about 0.005 mm apart, and twenty-five hook- 

 lets and over may be counted in a single trans versejspiral. There is some 

 variety in the shape oi the hooks on the basal enlargement. On its outer 

 part they are, in the main, straight and slender. Toward the inner side 

 on the anterior slope there are about five spiral series in which the 

 hooklets are placed close together side by side. These booklets stand 



