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



which approach more or less the niedio-ventral line. The ambulacra! vesicles of 

 the processes (PI. XLII. fig. 3) resemble large sacks, from 10 mm. to 15 mm. long, 

 which hang freely into the peritoneal cavity. A number of more or less spacious 

 cavities and lacuna? which are found in the perisoma ought probably to be considered as 

 belonging to the water-vascular system. The reproductive organ (PL XLVI. fig. 1) 

 is composed of numerous bundles of cseca forming two fascicles, separated from one 

 another by the medio-dorsal mesentery ; its common efferent duct opens externally at 

 the top of the above-mentioned genital process, w T hich is situated immediately behind 

 the pores of the madreporic canal ; the organ attains a length of 40 mm., and its walls 

 contain scattered spicula. 



As the above description is taken from the largest individual, obtained at Station 

 209, it is necessary to note the peculiarities which characterise the specimens from the 

 other localities. Those dredged at Station 219 attain a comparatively small size, 

 the largest measuring about 80 mm. in length ; their dorsal processes are not very 

 numerous and are disposed in a single slightly irregular row along each ambulacrum ; 

 one of the individuals has only twelve tentacles, which evidently must be regarded as 

 an abnormity ; the large wheels are more numerous than in the large specimen dredged 

 at Station 209. As is pointed out above, the individuals from Station 192 differ slightly 

 from the typical form ; their pedicels are not so obviously arranged in double rows, and 

 only two distinct rows of dorsal processes are present along each ambulacrum ; their 

 deposits are made up of an enormous number of dichotomously branched bodies, which 

 are not aggregated in such masses as to form white spots ; their small and large wheels 

 are very scattered. The alimentary canal, which is uninjured in these individuals, has 

 no cloaca of importance. 



Pannychia, 1 n. gen. 



Tentacles twenty, rather large and non-retractile. The lateral ambulacra of the 

 ventral surface with large pedicels, disposed in a single row all along each side of that 

 surface. The odd ambulacrum with a double row of pedicels. The dorsal surface with a 

 crowded series of very numerous, slender processes all along each side. Integument 

 with numerous wheels and small wheel-shaped plates. 



Pannychia moseleyi, n. sp. (PI. XVII.). 



Body elongated, almost cylindrical, several times longer than broad. Mouth anterior, 

 subventral. Anus posterior, terminal. Tentacles of nearly equal size ; their large, circular 

 discoidal ends bearing round their edge small rudimentary processes. Pedicels thirty along 

 the left side of the ventral surface, and twenty-nine along the right one. The odd 



Ni/g = night. 



