820 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 paxillae is only just beginning to show itself, the prominence 

 of the larger radial paxillae being only slightly larger than the rest. The armature of 

 the adambulacral plates is arranged in three regular 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 PI. 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 pedicellariae may occasionally be seen in the marginal series of a few of the large 

 paxillae 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 carination 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 paxillae to the form described as 

 Nectria ocellata, whilst in the character of the adambulacral armature it corresponds to 

 that of Nectria ocelli/era. On the other hand the small examples, whilst corresponding 

 to Nectria ocelli/era in the shortness of the ray, have the adambulacral armature similar 



