OUR KNOWLEDGE OF NEW ZEALAND HOLOTHURIANS. 107 



The anus is situated in a small depression at the apex of the conical tuil. 

 It is a small circular aperture surrounded by fifteen small papillae, three in 

 each radius. These papillse appear to be modified tube-feet. 



The body-wall itself is rather thin, but the circular muscles attached to it 

 are remarkably thick and form very conspicuous transverse bands between the 

 radial longitudinal muscles. Whilst on the body- wall the latter are single, 

 but as they run down the introvert each divides into two strips of muscle, 

 and each strip ends on the corresponding process of the bifurcate radial. 



The body-wall contains a large number of spicules which are almost 

 entirely in the form of small tables (fig. 13 a). These tables have an approxi- 

 mately oval base perforated by eight holes, arranged radially, four large 

 alternating with four small ones. The presence of these eight holes is very 

 constant, for in examining several hundred of the tables the only exception 

 found was the one represented in fig. 13 &, which is evidently abnormal. The 

 spire is formed of only two pillars supporting a cross-bar at their distal 

 extremities, and this bar usually bears about six spines. The dimensions 

 of an average-sized table are : — length of oval plate, 0'058 mm. ; breadth, 

 0-041 mm. ; height of spire, 0'017 mm. The size of these tables is, however, 

 very variable, the plate sometimes reaching 0"07 mm. x 0'019 mm. In a few 

 of them the spire is not developed, with the result that biscuit-shaped forms are 

 produced (fig. 13 c). These also have the usual eight perforations. 



In addition to these spicules of the body- wall, two more kinds occur in the 

 tube-feet. Each tube-foot is supported at its extremity by a circular convex 

 perforated plate, usually about 0*28 mm. in diameter, and resembling those 

 of Phyllopliorus dearmatus in form. Hound the edge of this end-plate is a 

 complete circle of irregular perforated plates (fig. 13 d) which support the rim 

 of the sucker. 



The mouth leads into a wide thin-walled pharynx supported at its anterior 

 end only by the calcareous ring (fig. 14), composed of ten simple plates, five 

 radial and five inter-radial (fig. Qa). The radials are oblong plates about 

 three times as long as they are wide and bifurcate at both ends. Each anterior 

 limb is abruptly truncated and exhibits a very slight further bifurcation. Each 

 posterior limb tapers to a pointed extremity attached to the end of the corre- 

 sponding inter-radial. These latter are A-shaped pieces, whose posterior 

 extremities turn outwards and thicken slightly at their ends, where they are 

 attached to the radials, as shown in the figure. 



The retractor muscles are attached partly to the anterior limbs of the 

 radials and partly to the pharynx-wall itself. Each runs from its pharyngeal 

 attachment to the corresponding longitudinal muscle, and is inserted some- 

 what in front of the middle of the body (in its retracted state). 



The posterior part of the pharynx narrows rapidly into an intestine (fig. 14, i.) 

 which does not vary much in structure throughout its whole length, there 



