REPORT ON THE CALCAREA. 6:3 



is directed towards the closed end of the animal, and only near the gastric openings their 

 disposition becomes irregular. 



Triradiate spicules of (he parenchyma. — Like those in Leuconia saccharaia in most cases regular, 

 but with rays not exceeding 045 mm. in length, usually still shorter (03 mm. and less). 

 In the first case the proportion between the leDgth and the thickness of the rays is like 

 Lcuconia saccharata 10:1 ; the rays of the smaller spicules are more slender, the corru- 

 sponding proportion varying from 12:1 to 20 : 1. The sagittally and irregularly dif- 

 ferentiated triradiate spicules of the parenchyma are too rare to be of any systematic 

 significance. 



Dermal triradiate spicules.- — Not differing from those of the parenchyma, and showing the same 

 variations with respect to size and slenderness, with only this distinction that the cases 

 of sagittal differentiation — the lateral rays growing more or less curved forwards — are 

 more numerous. 



Dermal quadriradiate spicules, — Rare. Sagittal ; basal and centripetally directed apical ray 

 straight, lateral rays curved forwards, often undulating ; all rays tapering from the base 

 to approximately sharp points, rarely longer than 04 mm., with a diameter of - 03 mm. 

 to 0'04 mm. 



Colour. — Violet-greyish. 



Habitat. — Station 149, off Kerguelen Island ; January 29, 1874 ; depth, 70 fathoms. 



Leuconia loricata, n. sp. (PL II. fig. 2 ; PI. VII. figs. da-Gb). 



The chief characters of this species, represented in the Challenger collection by a single 

 specimen, 30 mm. long, and 8 mm. broad, are the following: — (1) a strongly-developed 

 cortex - 5 mm. thick, the width of the whole wall being 2 mm., consisting of several 

 parallel layers of sagittal triradiate spicules ; (2) a quite irregular disposition of the 

 parenchymal spicules, only those which are near the inner surface lying more or less 

 parallel to it ; (3) minute spined acerate spicules scattered everywhere in the body, but 

 chiefly coating the inner surface. The structure of the canal system presents no 

 deviations from the general type. 



Skeleton. — The skeleton consists of minute spined acerate spicules, of triradiate spicules 

 of the parenchyma, of cortical triradiate, of cortical stout and linear acerate, and of 

 acerate spicules of the peristome. 



Spined acerate spicules. — The modifications of their form, and the intermediate stages between 

 them and common spindle-shaped minute acerate spicules, although rare in Leu* 

 loricata yet still to be found, are given on PI. VII. fig. 6a-6a"". Their average length is 

 - 025 mm, with a diameter of 0'002 mm, Numerous on the inner surface, they Rre very 

 rare in the parenchyma and in the cortex. 



