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



it is narrower anteriorly and wider posteriorly where the limbs articulate ; in neither of 

 these segments are any spiny epimera developed. 



The abdominal shield is preceded by a narrow free abdominal segment ; it is more 

 or less oval in form and rather wider anteriorly than posteriorly ; the anterior region 

 is very convex, the posterior region, which terminates in a somewhat truncated margin, 

 is less so. 



As in all other species of the genus the anus opens posteriorly at the extremity and 

 is surrounded by soft folds of tissue. Fig. 9 of PI. VI. 1 represents the caudal Bhield, 

 viewed from beneath, to show the large aperture of the anus (a) ; in this as in other 

 species the calcareous bar (6), which bounds the anus anteriorly, is in reality the 

 homologue of the ventral plate of the last segment of the abdomen, and is of course 

 not the telson bent downwards. 



Several of the appendages have fortunately been preserved intact. 



Of the fourth segment of the thorax the left hand appendage is complete ; it is 

 shown in fig. 7. 



The whole appendage about ecpials the body of the animal in length ; like the 

 succeeding appendages it appears to be almost destitute of hairs or spines ; the first 

 two joints are moderately long and subecpial ; the third is short, rather less than half 

 the length of either of the preceding ; the fourth and fifth are long and slender, and 

 the sixth joint forms a slender terminal claw. The appendages of the remaining 

 segments of the thorax are of almost exactly the same shape and of about the same 

 length, so that no special description of them is necessary. 



The posterior thoracic appendages of this species, therefore, are like the anterior 

 appendages, and are not modified into foliaceous swimmerets (as in Munnop>sis). Like 

 the body itself the appendages appear to be very fragile ; the integument is very thin 

 and brittle, and evidently much calcified. 



The abdominal appendages do not present any remarkable features, except their 

 small size, corresponding to the small size of the caudal shield; this being the case the 

 thinness of the test of the animal may facilitate respiration by the general body 

 surface. 



The uropoda are broken on one side of the body but intact on the other ; they are 

 styliform, only consisting of one ramus ; the appendage is made up of three joints, a 

 stouter proximal joint, and a more slender distal joint, shorter as well as thinner than 

 the preceding one with which one or two long hairs articulate. 



In the figure which illustrates the species (fig. 6) I have indicated the alimentary 

 canal, or rather its contents, to show the comparative transparency of the body. 



Station 158, south-west of Melbourne, March 7, 1874 ; lat. 50° 1' S., long. 123° 4' E.; 

 1800 fathoms; bottom temperature, 33°"5 F.; Globigerina ooze. 



This figure refers to Ischnosoma bacilloides, but the structures depicted are the same in both species. 



