REPORT OX THE CALCAREA. 69 



;ui interesting peculiarity in the histological character of the pavement cells of their 

 surface, these cells, as well as the granules of their protoplasm, being here incomparably 

 larger than usual (fig. 8). Of the generative products I found in the specimen only young 

 ova. In its spiculation the species shows a great affinity to Leucetta clathria H. (sp.), 

 hut the form and dimensions of the spicules of the parenchyma are so very different, thai 

 the establishment of a new species is necessary. 



Skeleton. — The skeleton consists of gastric and parenchymal quadriradiate, of cortical 

 quadriradiate spicules, disposed like those in Leucetta imperfecta, and of cortical tri- 

 radiate spicules. 



Gastric and parenchyma! quadriradiate spiodis. — Usually regular; rays smooth, tapering 

 from base to approximately sharp points, facial rays straight, apical ray either straight or 

 undulating, length varying from O05 mm. to O'l mm., the proportion between the length 

 and the thickness being 10 : 1. Some of them occasionally become sagittal, the angle 

 between the basal and each of the lateral rays becoming more acute; in the parenchyma 

 such sagittal quadriradiate spicules show an inclination to lose their apical ray. 



Cortical quadriradiate spicules, — Regular or sagittal, the angle between basal and lateral rays 

 varying from 120° to 112°; all rays smooth, tapering from the base to sharp points, the 

 proportion between the length and the thickness being 10 : 1 ; basal and apical rays straight; 

 lateral rays either straight or slightly curved; facial rays rarely longer than - 8 mm., 

 length of the apical ray inconstant, varying from 0'6 mm. to 2 mm., its free end projecting 

 occasionally from the inner surface. 



Cortical triradiate spicules. — Regular; rays conical, tapering from base to sharp points, - 45 mm. 

 long, with a diameter of 00375 mm. ; near the osculum these triradiate spicules become 

 smaller nnd sagittally differentiated, adopting the form of the oscular triradiate spicules of 

 Leucosolenia poterium (?), Leuconia dura, &c. 



Colour. — Greyish. 



Habitat. — Off Kerguelen, January 1874; depth, 10 to 100 fathoms. 



Leucetta hackeliana, n. sp. (PI. II. fig. G ; PI. VIII. figs. 1-6). 



This species, which I dedicate to the illustrious author of the Kalksehwamme, shows, 

 like Leucetta ecru, a very close relation to Leucetta clathria, II., but the differences 

 in spiculation are still considerable enough to separate these two forms into different 

 species. The cortical quadriradiate spicules are in Leucetta hackeliana strikingly 

 rare, their apical ray never projects with its free end from the outer surface; the gastric 

 and parenchymal quadriradiate spicules are, although similar in size to those in Leucetta 

 clathria, yet of quite different outline, and finally, Leucetta clath via was found in the form 

 of a mouthless colony (Kalkschwamme, ii. p. 159), while all the specimens of my Leucetta 

 hcecheliana are provided with an osculum, the collar of which possesess its own skeleton, 

 different from those of the cortex and of the parenchyma. Three individuals of this 



