107 



5 well defined segments. Genital segment considerably dilated, almost quadrate 

 in form, and, as a rule, containing on each side an oblong oval spermatophore. 

 Caudal rami comparatively shorter than in female. Anterior antennae very 

 strongly hinged. 



Colour whitish grey, with a very slight pale yellow tinge. 



Length of adult female scarcely attaining 1 mm.; that of male 0.78 mm. 



Remarks. This form was considered by Scott and also "by myself as 

 only a variety of E. longicauda. I am however now of opinion that it should 

 more properly be regarded as a separate, though closely allied species. 



Occurrence. I have met with this form in many different places of 

 our coast, and have always found its characters constant. It is, unlike E. longi- 

 couda, a true deep-water form, occurring in depths ranging from 20 to 50 

 fathoms, never in the littoral zone. 



Distribution. Scottish coast (Scott). 



Siphonostoma. 

 Fam. Ascomyzontidae. 



Gen. Rhynchomyzon, Giesbr. 



85. Rhynchomyzon falco, Giesbr. 

 (PI. LXXI). 



Rhynchomyzon falco, Giesbrecht, Die Asterocheriden des Golfes von Neapel, p. 102, 



PI. 5, figs. 2840. 



Specific Characters. Male. Body comparatively robuste, with the 

 anterior division rather broad in the middle and somewhat depressed. Cephalic 

 segment very large, about twice as long as the remaining part of the trunk, 

 and, seen dorsally, triangular in outline, being gradually contracted anteriorly, 

 with the extremity narrowly truncated; lateral corners slightly produced, biden- 

 tate. Rostrum very strong, falciform, and curved downwards. The 3 suc- 

 ceeding segments, like the cephalic segment, somewhat raised dorsally at the 

 hind edge, and having the lateral corners produced to triangular recurved 

 lappets. Last trunkal segment, as usual, much smaller than the preceding ones, 



