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



of the joint; there appeared to be three spines on the outer side and only two on the 

 inner; the largest spine of either side was placed just before the articulation with the 

 third joint ; this is short, about one-fourth of the length of the preceding ; the two distal 

 joints of the peduncle are long and slender, and have, like the third joint, no spines ; the 

 last joint of the peduncle is longer as well as more slender than the fourth ; the flagellum 

 is multiarticulate. 



The first pair of thoracic appendages were stouter and shorter than the following ones. 

 The remaining thoracic appendages (fig. 4) are similar to each other; they are long ami 

 slender; the posterior pairs are not distinctly longer than the anterior pairs. They are 

 furnished with numerous spines of varying length, which ure mainly developed upon the 

 proximal joint of the limb and disappear after the second. The spines are borne upon 

 projections of the limb ; the spine itself is distinguishable from the base, which is an 

 outgrowth of the limb, by its transparency and yellow colour ; the extremities of many of 

 the lateral spines of the segments are tipped with a minute transparent yellow point in 

 a similar fashion to the spines of the limbs. 



The thoracic limbs terminate in a single elongated claw-like joint. 



The uropoda (fig. 5) consist of a single stout conical joint with a few hairs scattered 

 over its surface. 



Ischnosoma spinosum is to be distinguished from its immediate allies, Ischnosoma 

 bispinosum and Ischnosoma quadrispinosum, by the great development of spines upon 

 the body and the appendages ; the numerous other points of difference may be gathered 

 from the foregoing description. 



Station 78, off the Azores, July 10, 1873 ; lat. 37° 26' N., long. 25° 13' W.; depth, 

 1000 fathoms; volcanic mud. 



Ischnosoma bacillus, F. E. Beddard (PI. VI. figs. 6, 7). 



Ischnosoma bacillus, F. E. Beddard, Proc. Zool. Soc. Lond., 188G, pt. i. p. 98. 



This very remarkable Munnopsid closely resembles the species next to lie described ; 

 it consists only of a fragment ; the head and the first three thoracic segments are entirely 

 wanting. The second species, which I have named Ischnosoma bacilloides on account of 

 its close similarity to Ischnosoma bacillus, consists likewise of a fragment which includes 

 precisely the same segments, viz., the four posterior thoracic segments and the abdominal 

 shield. 



The name " bacillus" was suggested by the rod-like form of the bod}-, which witli its 

 elongated segments recalls the form of the body in the " walking-stick insect " Bacillus. 

 Although this species, as well as the next, is so imperfect, I have no hesitation in assigning 

 both to the genus Ischnosoma by reason of the oval caudal shield with its Btyliform uropoda 

 and the metamorphosis (in the female) of the first pair of appendages belonging to the 



