REPORT ON THE HEXACTINELLIDA. 213 



tlie parench}Tna and of the basal tuft were exactly similar to those above described. The 

 skin was unfortunately wholly absent, so that nothing further could be ascertained as to 

 dermal skeleton. 



A third specimen, which in my opinion belongs to this species, Hyalonema 

 thomsoni, is deposited in the Berlin Zoological Museum. It is labelled as Hyalonema 

 lusitanicum, Socage (?), was collected by Wyville Thomson off the West Hebrides, 

 and is numbered 405. This splendid specimen has a total length of 21 cm., and the 

 body proper, which occupies 9 cm., has a maximum breadth of 3 cm. I have figured it in 

 its natural size on PI. XXXIV. fig. 1. The apical cone projects — 2 cm. in length — from 

 the centre of the truncated terminal surface, which exhibits four cruciately disposed radial 

 septa and interjacent apertures, and resembles exactly the superior surface of the speci- 

 men figured by Marshall. Below the somewhat sharply angular projecting lateral margins 

 of this smooth terminal surface, which is not covered by a dermal sieve-network, the 

 body exhibits a slight annular constriction but curves outwards again below the middle, 

 and is finally conically narrowed towards the lower end. Below the somewhat rounded 

 off" annular basal jjad, there is an encrustation (6 cm. long) of Palythoa, and from this the 

 basal tuft is prolonged downwards (PI XXXIV. fig. 1). 



In the parenchyma, besides medium-sized, smooth, regular oxyhexacts and numerous 

 smooth, straight, or gently curved oxydiacts, with or without central nodes or tubercles, a 

 large number of small oxyhexacts with straight, somewhat roughened rays occur, similar 

 to those which we have already described and figured in the smaller specimens (PI. XXXIV. 

 fig. 4). 



The dermal skeleton exhibits the same smooth hypodermal oxypentacts and somewhat 

 long, narrow pinuli, with moderately long, slightly spinose, basal rays, as we have already 

 described in the smaller specimens. The amphidiscs also essentially agree in size and 

 form with those above described and figured (PL XXXIV. figs. 2, 3, 5, 7, 8,), and differ 

 only in this, that the largest amphidiscs with short, narrow umbel rays have, as a rule, not 

 six but eight rays. The substantial toothed spicules of the basal pad and the long spicules 

 of the root-processes essentially resemble those of the above forms ; occasional, slight, 

 and inconstant differences seem to me to be simply individual, conditioned by the large 

 size, and in no way of specific importance. 



The superior terminal surface is in this specimen much better preserved than in the 

 smaller forms, so that the essential agreement between the covering membrane and the 

 external skin is demonstrable, except that the autodermal pentact pinuli are somewhat 

 narrower and longer than in the former. The same enveloping layer extends for some 

 distance into the system of efferent tubes. 



Near the basal pad numerous more or less long diacts occur in the parenchjTna, 

 and do not run out at their ends into smooth points, but are somewhat thickened 

 and spinose before finally terminating in conical points. At the middle point of 



