66 THE VOYAGE OF H.M.S. CHALLENGE!:. 



sagittal ones in my Leuconia dura proves the constancy in the presence of the osculum, 

 and thus justifies the establishment of a new species. 



Colour. — Yellowish and greyish. 



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

 Station 186, September 8, 1874; lat. 10° 30' S., long. 142°-18' E. ; Torres Strait, 

 Australia ; depth, 8 fathoms ; coral sand. 



Pericharax, n. gen. 

 Leuconidas with distinct subdermal cavities. 



Pericharax carteri? n. sp. (PI. II. fig. 5 ; PL VII. fig. 8). 



The species is represented in the collection by a whole specimen and a fragment of 

 another. The first is shown on PI. II. fig. 5. It reaches 40 mm. in length, with a 

 maximum diameter of 22 mm., the thickness of the walls being 5 mm., in the second 

 specimen not exceeding 3 mm. The outer surface is smooth, the inner roughened by 

 the apical rays of the gastric quadriradiate spicules. From Pericharax cucumis 

 (Leucandro. cucumis, H. — Kalkschwamme, ii. p. 205) the species can be distinguished 

 by the following characters : — 1, the skeleton of the parenchyma and of the subdermal 

 cavities consists not of quadriradiate but of triradiate spicules ; 2, the subdermal spicules 

 are not larger than those of the parenchyma, but equal to some of these and smaller as 

 compared with others. 



The species itself is to be subdivided into two varieties ; the gastric spicules and 

 those of the parenchyma are of the same size and form in both specimens, but in one 

 the skeleton of the subdermal cavities consists of regular triradiate spicules, not differing 

 from the smaller spicules of the parenchyma, in the other of sagittal and irregular tri- 

 radiate spicules, although of the size of the smaller triradiate spicules of the parenchyma, 

 yet of a different form. The first variety may be named " homor aphis" the second 

 •• heteroraphis." In both these varieties the " gastric ostia" are very large, their diameter 

 reaching 075 mm. The exhalent canals are also of considerable dimensions, their surface 

 almost in all their length being armed with quadriradiate spicules. 



One specimen, var. homoraphis, proved to be sterile, in the other I found ova of an 

 extraordinary size, their diameter being 0"3 mm. on an average 



Shirt, ,u. — The skeleton consists of regular gastric quadriradiate spicules, following the 

 course of the invaginations of the inner cavity; of larger and smaller regular triradiate 

 spicules of the parenchyma, and of dermal triradiate spicules, as well as of those of the 

 subdermal cavities, regular in one variety, sagittal and irregular in the other. 



1 I dedicate this species to Mr. H. J. Carter, F.B.S., as a token of my deep respect for his scientific labours. 



