4 POKCUPINE ’ DEEP-SEA DEEDGING-EXPEDITIONS. 
7o5 
of muscle which fill them seem disproportionate to the rather small and very delicate 
and fragile spines. 
There are two forms of pedicellarise : one (Plate LX1I. fig. 5), which occurs in small 
number in rows obscurely parallel with those of the larger spines, approaches in form 
the ordinary tridactyle pedicellarise of the Echinidae, though presenting some special 
characters ; the second is a peculiar form of the so-called “ ophiocephalous ” pedicel- 
lariae, peculiar, so far as I am aware, to the Echinothuridae and the Diadematidae (Plate 
LXII. fig. 6). The head of this pedicellaria is three-valved and very minute — in the 
present species not more than - 5 millim. in length. The distal end of the valve is broad 
and thin, and the three valves when closed meet only at the edges, and leave a small 
triangular space in the centre. The proximal end of each valve is truncated, ending in 
a triangular fluted plate. These three plates, meeting in the centre, form the base of 
the head of the pedicellaria, and are attached beneath to a gelatinous column about 
equal in length to the valve of the pedicellaria, which intervenes between the head and 
the end of the delicate stem. About the middle of each valve the fenestrated calcareous 
plate of which it is formed appears to curl inwards on each side, and the valve becomes 
double, forming a small conical chamber. A triangular keel runs from the inner angle 
of the basal plate up the face of this chamber in the middle line nearly to the point 
where the chamber ceases and the plate becomes single. The calcareous rod supporting 
the pedicellaria is of considerable length, from 3 to 5 millims. Pedicellarise of this 
description are excessively numerous, scattered apparently irregularly all over the test ; 
they are particularly abundant on the lower surface towards the edge of the peristome. 
The tube feet on the lower surface of the test have their walls supported by large, 
broad, fenestrated plates (Plate LX1II. fig. 8), and are provided with a sucker with a well- 
developed calcareous rosette of four or five pieces. The tube feet on the apical surface 
of the test are much longer, conical, and come to a point : these are probably subser- 
vient to the function of respiration only. 
The auriculae are well developed and strong, though not very heavy. The two sides 
meet in a complete arch. Each pair of adjacent auriculae are connected together by a 
raised calcareous ridge, which passes across, soldered to the interambulacral plates (Plate 
LXIII. fig. 1). The jaws are short and very wide, forming together a wide depressed 
pyramid. The two sides of each jaw-pair are broad and wing-like, and their outer angles 
present scarcely a trace even of epiphyses. The teeth are simply channelled, and come 
to a fine sharp point, as in some species of Diadema. 
The specimen from which the above description was taken, the only one procured 
with the exception of some fragments, was torn open and the soft parts were greatly 
injured. The ovaries were long and narrow, running, closely attached to the test, from 
the ovarial opening to the periphery, along the middle line of the interambulacral space. 
The colour of the test is a pale grey flecked with purple. The tube feet are purple, and 
the spines are nearly colourless. 
Locality. One imperfect specimen from a depth of about 500 fathoms, lat. 59° 43' N., 
MDCCCLXXIV. 5 G 
