()<> THE VOYAGE OF H.M.S. CHALLENGER. 



from 110° to 115°; lateral rays undulating, forming one with the other an angle of about 

 170°; apical ray curved, rarely longer than (H mm. These quadriradiate spicules are con- 



ited by intermediate stages with the larger triradiate spicules of the parenchyma, which 



are furnished also here and there with short apical rays. 



'/', , adiatt tpit ules of the parenchyma. — Of two kinds; larger, sagittal, their basal ray in most 

 cases directed centrifugally, and smaller, either regular or sagittal or irregular, scattered in 

 the parenchyma without any order. Larger triradiate spicules. — All rays in the same 

 plane and of the same diameter (0-015 mm.), occasionally rather thicker ; basal ray straight, 

 like lateral rays tapering from the base to a sharp point, length O'o8 mm. on the average ; 

 lateral rays either straight or more or less curved, often undulating, each forming with 

 basal ray an angle varying from 115° to 125°, average length 02 mm. Smaller triradiate 

 spicules. — Forin variable (PL VII. fig. id—Id'") ; length of rays not exceeding 0'075 mm., 

 the proportion between the thickness and the length being 1:10; not numerous. 



lh rmal triradiate spicules. — Of exactly the same size and form as the larger triradiate spicules 

 of the parenchyma, the only distinction being that the angle between basal and each lateral 

 ray is more constant (120°), and that the lateral rays are usually neither straight nor un- 

 dulating, but slightly curved. 



Colour. — Dirty yellowish. 



Habitat. — Station 145, December 27, 1873; lat. 46° 40' S., long. 37° 50' E.; off 

 Prince Edward Islands; depth, 150 fathoms. 



Leuconia crucifera, n. sp. (PL VII. figs. 5a-5d). 



This species is represented in the Challenger collection by a single fragment belonging 

 to the inferior part of the animal. The fragment is of compressed form, 10 mm. long, 

 with a maximum diameter of 8 mm. The thickness of the walls is - 8 mm. The outer 

 surface is bristly, the inner surface slightly roughened by the apical rays of the gastric 

 quadriradiate spicules. These are all more or less cruciform, all the rays lying in the 

 same or almost in the same plane. By this character the species can be very easily dis- 

 tinguished from all other Lcuconidse. There are indeed some forms which, like Leuconia 

 nivea, Leuconia johnstonii, &c, possess cruciform quadriradiate spicules also; but in 

 these species these are alw T ays minute, while here in Leuconia .crucifera, on the contrary, 

 they are of considerable size. 



Leuconia crucifera and Leucosolenia blanca are of particular interest as forms inhabit- 

 ing the greatesl depth (450 fathoms) from which Calcarea have been hitherto obtained. 



Skeleton. — The skeleton consists of gastric quadriradiate, of parenchymal triradiate, 

 of dermal triradiate, and of stout acerate spicules, piercing the parenchyma obliquely, and 

 projecting with theirfree end from the outer surface,and of slender acerate spicules, scattered 

 here and there on the outer surface in small bundles. 



