50 THE VOYAUE OF II. M.S. CHALLENGER. 



chynia spicules of approximately the same dimensions, characterised by a rudiment of 

 the fourth ray, by the undulating lateral rays, and by the comparative length of the basal 

 ray -twice as long as the lateral. I cannot decide whether these are modified triradiate 

 spicules of the parenchyma or of the subgastric region, or quadriradiate spicules of the 

 parenchyma grown considerably larger. They are not numerous. 



Dermal triradiate spicules. — Sagittal; all rays in the same plane, either rather cylindrical 

 or tapering from the base to a sharp point ; basal ray straight, lateral rays curved out- 

 wards, each forming with basal ray an angle of about 120°; absolute length very variable, 

 in most cases lateral rays 0'4 mm. ; basal ray 03 to 04 mm., the proportion between the 

 length and the thickness of the rays being 20 : 1. 



Large acerate spicules. — Usually not longer than 6 mm., occasionally reaching 10 mm. (var. 

 goliath — immediately under the osculum, projecting from the inner surface), with n 

 diameter never exceeding - 05 mm.; either spindle-shaped, tapering at either end from the 

 centre to a sharp point, or lanceolate ; occasionally of irregular outlines, one end being 

 sharp-pointed, the other truncated or irregularly spherical. 



Linear acerate spicules of the peristome. — Attaining a length of over 5 mm., with a diameter of 

 O'OOo mm., either straight or slightly curved. 



Minute acerate spicules. — Spindle-shaped, tapering from centre to sharp points, rarely exceeding 

 0125 mm. in length, and 0'0025 mm. in diameter. 



Colour. — White, cream-white, and dirty yellowish. 



Habitat. — Station 36, April 23, 1873, off Bermudas; depth, 32 fathoms; mud. 

 Station 209, January 22, 1875 ; lat. 10° 10' N., long. 123° 55' E. ; Philippine Islands; 

 depth, 95 to 100 fathoms ; mud. 



Leuconkt typica, n. sp. (PI. VII. figs. 2a-2c). 



The three specimens representing this species in the Challenger collection are to be 

 referred to two varieties with the following diagnoses : — 



Leuconia typica, var. tuba : tubular, gastric cavity narrow elongated ; apical rays of 

 gastric quadriradiate spicules not longer than 0'06 mm., usually still shorter ; fine linear 

 acerate spicules reaching - 3 mm. in length. 



Leuconia typica, var. massa : lumpy, stout, massive, the longitudinal axis shorter than 

 the transverse ; gastric cavity considerably reduced, calyciform ; apical rays of gastric 

 quadriradiate reaching 0'1 mm. in length ; fine acerate spicules not longer than - 15 mm. 



Both the specimens of the variety tuba are 25 mm. long, the average thickness of the 

 walls being 3 mm. The specimen of the variety massa is 8 mm. high, 18 mm. broad at its 



