1464 THE VOYAGE OF H.M.S. CHALLENGER. 



Length. — From the front of the head to the end of the third pleon-segment the 

 specimen measured almost half an inch. 



Locality.— Station 243, June 26, 1875; North Pacific; lat. 35° 24' N., long. 

 166° 35' E. ; deep tow-net. One specimen, female with numerous eggs. 



Remarks. — On various parts the specimen has slightly swollen blotches, probably 

 caused by some parasite. 



In Dithyrus faba, Dana, the first joint of the fourth peraeopods is represented with 

 the terminal part outdrawn as in this species, but it would be rash to identify the two 

 on the existing evidence. Whether Risso's Typhis ovoides and Spence Bate's Thyropus 

 ovoides are really the same species as Claus' Eutyphis ovoides is still perhaps open to 

 question. Platyscelus intermedins, G. M. Thomson, from New Zealand, seems scarcely 

 if at all distinguishable from Platyscelus ovoides. 



Platyscelus armatus (Olaus) (PI. CLXXXIL). 



1879. Eutyphis armatus, Claus, Die Gathmgen und Arten der Platysceliden, p. 10. 



1887. Euti/phes armatus, Bovallius, Systematical List of Ampli. Hyper., Bihang till K. Svensk. 



Vetensk.-Akad. Handl., Bd. 11, No. 16, p. 45. 

 1887. Eutyphis armatus, Claus, Die Platysceliden, p. 36, Taf. ii. figs. 3-15. 



Head broad, with downward bent, triangular rostrum, the apex of which is wedge- 

 like ; a depression crosses the front of the head just below the eyes and above the rostral 

 triangle; the pera3on is of great breadth, its first two segments extremely short, especially 

 at the centre ; the first three segments of the pleon with oblique lateral depressions ; the 

 fifth and sixth segments and the telson coalesced, forming an equilateral triangle, the 

 sides of which neatly fit the straight section of the hind margin in the first joint of the 

 fourth peraeopods ; the apex of the first joint of the third peraeopods reaches the rostral 

 point of the head, the animal being thus able to assume a compact egg-shape, but having 

 the side-plates of the fourth, fifth, and sixth peraeon-segments projecting, those of the fifth 

 segment most prominently and sharply. 



Eyes large, divided by a narrow central line, occupying all the surface of the head 

 except the front portion already indicated ; in each eye a lower division is indistinctly 

 marked off from the much larger dorsal, the lower division not reaching as far as the 

 rostrum. 



Upper Antennse (of the male). — The first joint of the peduncle longer than broad, the 

 second short ; the first joint of the flagellum much longer than the peduncle, strongly 

 bent, the convex margin thickly beset with long hair-like filaments, not itself projecting 

 beyond the base of the next joint, which is about twice as broad as long, carrying a few 

 pairs of filaments ; the next joint shorter, and not half as wide, with a pair of filaments 

 below the centre, then narrowing ; the fourth joint not present in the specimen examined. 



