520 THE VOYAGE OF H.M.S. CHALLENGER. 
Young Phases.—In a small specimen in which R=23 mm. (about), and r=10 mm., 
the rays are much shorter and flatter, broader at the base and comparatively less tapering ; 
the elevated character of the paxille is only just beginning to show itself, the prominence 
of the larger radial paxille being only slightly larger than the rest. The armature of 
the adambulacral plates is arranged in three recular and distinct rows, with three spinelets 
or granules in each; the furrow series being the longest and most spiniform, and the 
second series slightly oblique. The actinal surface is remarkable for the large size, 
distinctness, and regularity of the plates. This example is drawn on Pl. LV. figs. 3 and 4. 
In a slightly earlier stage the rays are still flatter and the abactinal plates cannot be 
said to be tabulate or paxilliform at all. At the base of the rays there is a slight pro- 
minence, which is emphasised by a depression in the median interradial line. Small 
incipient pedicellaria may occasionally be seen in the marginal series of a few of the large 
paxillee in this and the above-mentioned stage. This is particularly interesting as their 
presence in the adult is very doubtful and obscure, but traces may be detected here and 
there of their former existence, as shown in this stage. 
At a still earlier stage, when R=13 mm., r=6 mm., the prominence at the base of 
the rays above mentioned extends as a median carination throughout the ray, and cul- 
minates near the centre of the disk in a slight conical peak, in the centre of which the 
anal aperture is situated. 
In the smallest example, which measures R=10 mm., r= 5'5 mm., the flatness of the 
rays and the median ecarination are striking features. The abactinal plates are low, 
circular, and with moderately large papular interspaces; their granulation is uniform and 
rather widely spaced. The terminal plate is large and tubercular; and bears two stumpy, 
conical, spiniform papillae. The character of the whole abactinal area is essentially Penta- 
gonastrid, and bears no resemblance to the strikingly marked features of the adult 
Nectria. The marginal plates are broad and well-developed both on the abactinal and 
actinal areas. The armature of the adambulacral plates represents three series, the 
furrow series and that next behind having three spinelets or granules in each, whilst the 
outer series is often represented by only one. The obliquity of the median series is very 
considerable, the adoral spinelet of the series being often in the place of a spinelet of the 
outer series. In the furrow series there is a tendency for the adoral spinelet to be rather 
less than the others, and on the larger plates on the inner half of the ray the rudiment of 
a minute fourth spinelet may be present on the edge of the plate behind the adoral 
furrow spine. 
Remarks.—It will be seen from the foregoing that the adult example conforms in the 
length of the ray and in the shape and granulation of the paxille to the form described as 
Nectria ocellata, whilst in the character of the adambulacral armature it corresponds to 
that of Nectria ocellifera. On the other hand the small examples, whilst corresponding 
to Nectria ocellifera in the shortness of the ray, have the adambulacral armature similar 
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