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



well as by giving off a number of caecal prolongations, which run into the connective 

 tissue of the perisoma ; those cavities which belong to the pedicels and processes of the 

 ventral lateral ambulacra lie, of course, very close side by side, and mostly overlap one 

 another. In order to get a correct idea of their position and general appearance it is very 

 advantageous to inject into the pedicels and processes. 



The digestive tract is throughout the whole of its long course attached to the inside of 

 the dorsal perisoma by a fenestrated continuous mesenteric membrane. The cloaca is of 

 little importance. The reproductive organ (PI. XL VI. figs. 6 and 7) is made up of two 

 fascicles of unbranched, elongated, caecal sacks, communicating anteriorly, where they are 

 attached, one fascicle on each side of the dorsal mesentery, with a single efferent duct. 

 In some individuals each fascicle consists of only three to four or usually eight to nine 

 caeca, which in comparison with the length of the body are short ; in other specimens 

 they are made up of a great number of very small caeca. Before finishing the descrip- 

 tion of this species it may not be out of place to point out the differences which dis- 

 tinguish the forms dredged at Station 157 from the others, and which possibly may appear 

 to be of such a nature as to justify their separation as at least a variety. We have then 

 to note the violet colour, which is peculiar to those specimens, the comparatively minute 

 length of the processes, and, finally, the firm construction of the calcareous plates and 

 their want of spines or other projections, this latter peculiarity being however common 

 to several individuals from other stations. 



Deima, Thdel. 



Dehna, Theel, Preliminary Report on the Holothuridse, pp. 4, 5. 

 Tentacles twenty (?), small and capable of being retracted within the mouth. The 

 lateral ambulacra of the ventral surface with large pedicels, disposed in a single row all 

 along each side of that surface, and with another series of very elongated, conical, rigid, 

 non-retractile processes, placed externally and above the pedicels all along each side of 

 the body and directed straight outwards. The odd ambulacrum naked. The dorsal surface 

 with processes, resembling those of the ventral lateral ambulacra, disposed in a single row 

 all along each of its ambulacra. Integument with crowded, irregularly rounded, 

 perforated plates, forming a rather hard skeleton. 



Dehna validum, Theel (PL XVIII. and PI. XIX.). 



Deima validum, Theel, Preliminary Report on the Holothuridie, p. 5. 



Body of an almost elliptical form, about once and a half as long as its greatest 



breadth. Mouth anterior, ventral. Anus posterior, ventral. Tentacles very small, 



perfectly retractile ; their terminal part with five to six small retractile processes. 



Pedicels eleven along each side of the ventral surface ; the posterior pair, behind the 



