REPORT ON THE CALCAREA. 57 



lower end, and the average thickness of its walls reaches 5 mm. In both varieties the outer 

 and inner surfaces are rough. In its spiculation the species shows a close relation both to 

 Leaconia multiformis and to Leuconia caminus (Leucandra caminus H.), but still the 

 differences are considerable. The main character separating the form in question from 

 Leuconia multiformis is the absence of sagittal subgastric triradiate spicules; by its 

 distinctly sagittal dermal triradiate spicules the species can be also very easily dis- 

 tinguised from Leuconia caminus. 



The round flagellated chambers in this species have particularly regular outlines, and 

 are smaller than in any other case, their diameter rarely exceeding 0'04 mm. In one 

 specimen of the variety tuba, I discovered many spermospores, but unfortunately it was 

 not well preserved. The specimen of the variety massa proved to be full of Amphi- 

 blastulaj. 



Skeleton. — The skeleton consists of gastric epiadriradiate spicules, quadriradiate spicule? 

 of the parenchyma, not differing how 7 ever, either in form or size, from those of the gastric 

 surface, triradiate spicules of the parenchyma, of dermal triradiate and of parenchymal 

 acerate spicules. 



Gastric quadriradiate spicules. — Basal ray straight, tapering from the base to a sharp point 

 usually shorter (O'lS mm.) and rather thinner than lateral rays, forming with each of 

 these latter an angle varying from 105° to 110° ; lateral rays more or less cylindrical, either 

 straight or slightly curved forwards, rarely exceeding 0225 mm. in length, with a diameter 

 of 0"015 mm. ; apical ray curved, more or less sharply pointed, in the var. tuba wedge- 

 shaped, leugth not exceeding 006 mm., in the var. massa reaching 01 mm. In both cases, 

 however, the length of the apical ray is variable, and there are amongst the quadriradiate 

 spicules many triradiate spicules also. 



Triradiate spicules of the parenchyma. — Most quite regular; rays straight, smooth, tapering 

 from the base to sharp poiuts ; reaching 0'75 mm. in length and - 065 mm. in diameter. 



lh , mal triradiate spicules. — Sagittal ; all rays of the same length, rarely exceeding 0'35 mm., 

 and of the same diameter (002 mm.), either tapering from the base to sharp points, 

 or of a more cylindrical form; basal ray straight, lateral rays curved forwards, forming 

 each with basal ray an angle of about 115°. 



Acerate spicules. — In the walls of the body (sparsely scattered here and there in the 

 pareuchyma, either isolated or in groups) fine, linear, straight, occasionally slightly curved, 

 reaching - 3 mm. in the variety tuba, not exceeding O'l mm. in the variety massa, diameter 

 0'001 mm.; near the osculum (var. tuba) piercing the wall in perpendicular direction, 

 either spindle-shaped or rather cylindrical, but sharp-pointed, straight or slightly curved, 

 01 mm. long, 0004 mm. in diameter. 



Colour. — Grey and dirty yellowish. 



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



(ZOOL. CHALL. EXP. I'ART XXIV. — 1883.) A:i 8 



