1891.] ^ BATHYBIASTER VEXII.LIFER, 229 



nerve-cord ; the ossicles are broad and strong ; the orifices for the 

 passage of the tubes are very deeply set, and the walls are so ex- 

 cavated as to form a pit which shelves inwards (Plate XXIV. fig. 2). 

 The adambulacral plates form projecting angles into the groove, and 

 the sides of this angle are at right angles to one another. Fixed on 

 the angle is a short spine and on either side there are generally four, 

 none of which are long, all of which are blunt, r.nd tlie three inner 

 of which are much broader than the fourth or outermost. Attached 

 to the spine at the angle is a blunt movable spine-like process, the 

 possession of which is the cause of the specific name \ and which 

 may be, indifferently, spoken of as a " vexillum." 



The single specimen has, as I have said, been unfortunately dried, 

 and I can say nothing, therefore, as to whether or not there are, as 

 in Bathybiaster pallidus, any elastic peduncle or strong muscular 

 fibres, while the membrane which, apparently, surrounded the spine 

 has shrivelled up in the drying. All that can be said, then, is that 

 the spine has a shallow groove along its upper end, and that its sides 

 are produced into fine denticulations (see Plate XXIV. fig. 1), which 

 recall, though they by no means equal, the denticulation of the 

 pedicellariae of B. pallidus. It is to be hoped that the species, when 

 next dredged, will be so preserved that a satisfactory and detailed 

 account of these spines may be made. 



The buccal apparatus is grooved, and projects well into the angles of 

 the mouth (Plate XXIV. fig. 5) ; it is closely covered with two rows 

 of about fifteen flattened stout subecjual spines ; the adambulacral plate 

 on either side of it is elongated and flat, not angulated where it pro- 

 jects into the groove (Plate XXIV. fig. .5). The next distal plate 

 has a long spine-bearing side and a much shorter side with no spines ; 

 the next has three spines on its shorter side, and in the next the 

 proximal and distal sides of the plate are almost subequal, in the 

 next they are equal. The dried ambulacral suckers are only slightly 

 conical. 



The intermediate plates in the interbrachial angle and along the 

 sides of the ambulacra are densely covered with squamiform granu- 

 lations (Plate XXIV. fig. .5), which become larger, looser, and more 

 erect near the angles of the mouth and near the sides of the ambu- 

 lacra. 



The two rows of marginal plates (supero- and infero-marginal) are 

 so closely approximated and covered with so uniform a granulation, 

 that it is almost possible to believe that there is a single and not a 

 double row of plates. They are strictly confined to the sides of the 

 arms, which they form alone ; the fact that the infero-marginal 

 plates practically take no part in forming the lower surface of the 

 arm may be explained by the flattening out of the ambulacral 



1 Described by Wyville Thomson in the following terms :— " The inner 

 spine oi' each comb on the side of the ambulacral groove is longerthan the oUiers, 

 and bears on the end a little oblong calcareous plate usually hanging Irom it 

 somewhat obliquely like a flag, with sometimes a rudiment of a second attached 

 to it in a gelatinous sheath, which makes it probable that it is an abortive 

 pedicellaria." 



