‘ PORCUPINE ’ DEEP-SEA DEEDGING-EXPEDITIONS. 
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elastic muscular fibres (Plate LXX. fig. 7) ; some smaller spines have small pointed 
elevations on the ridges (Plate LXXI. fig. 9) ; the secondary spines are very minute, 
paddle-shaped, and ornamented with crenated ribs (Plate LXX. fig. 8). The pedicel- 
larise are of two kinds ; the larger (Plate LXX. figs. 9, 9 a) are very peculiar in form. 
Three thick stems are articulated to a short stalk, and from each of these curves inwards 
a calcareous disk, bordered by an extremely elegant fringe of spines. The stems and the 
disks which represent the valves of pedicellarise of the ordinary form contain cavities 
which occupy the usual positions. The smaller pedicellarise resemble generally the 
smaller forms in the Echinidse. 
The general colour of Pourtalesia Jeffreys i is purple, rather light over the greater 
part of the test, but dark and rich from the accumulation of large pigment-spots round 
the raised border of the anterior surface, and especially about the posterior rostrum. 
The test of Pourtalesia is so remarkably thin that it will scarcely bear its own weight. 
Pourtalesia Jeffrey si differs from P. miranda, the species described by Prof. Alexander 
Agassiz, in having the test more uniformly cylindrical, and particularly in the form of 
the rostrum, which is much smaller than in P. miranda , with the usual depression much 
less marked. Another character which, in these aberrant forms having a tendency to 
the extreme modification of various parts, may have less importance than we should at 
first sight be inclined to assign to it, might be supposed to separate the two species 
widely : Prof. Agassiz states that in P. miranda the apical system is elongate, but not 
disconnected. In P. Jeffreysi the apical system is certainly disjunct, several extra plates 
which cannot be referred to the apical system being intercalated between its parts 
(Plate LXXI. fig. 3). 
A single specimen only of Pourtalesia Jeffreysi was dredged during the ‘ Porcupine ’ 
cruises. On one or two occasions, however, fragments of a thin purple test and frag- 
ments of spines, which we referred to this species, were sifted out of the mud. The 
shell is so excessively fragile that it may be regarded as a fortunate incident to have 
recovered any thing like a complete example. 
2. Pourtalesia phy ale, n. sp. (Plate LXX. fig. 11.) 
Test very much prolonged, almost tubular ; posterior rostrum more produced than 
in P. Jeffreysi ; anterior surface oblique to the axis of the test ; mouth-depression nearly 
central in the anterior end of the shell, surrounded by an oval raised rim or border. 
The specimen of P. miranda described by Prof. A. Agassiz is very small, but it already 
approaches P. Jeffreysi closely in form, and gives no indication of having undergone 
any very great change during the later stages of the process of growth. I therefore 
cannot imagine that the singular little urchin to which I have given provisionally the 
name Pourtalesia 'phyale is the young of the species previously described. Both of the 
two specimens procured by Mr. Gwyn Jeffreys at a depth of 1215 fathoms in the 
Rockall Channel are immature, and their characters are too undefined for satisfactory 
description. 
