78 THE VOYAGE OF H.M.S. CHALLENGER. 



Spicules. — (a) Megasclera; of one kind only, viz., long, smooth, slender, fusiform 

 styli (PI. XIX. figs. 6, 6'), size variable, about 0'8 by 0"028 mm., usually, however, 

 slenderer, {h) Microsclera; of two kinds; (1) large palmate isochelse (PI. XIX. figs. 

 6^, 6c), of the Esperella type, only with equal instead of unequal ends, length about 0"037 

 mm.; (2) very minute and slender sigmata, usually much contort, enormously abundant, 

 length about 0"013 mm.; (3) much larger, very slender sigmata (PI. XIX. fig. 6a). 



This is a very remarkable sponge, the most noticeable feature in which is the radiately 

 symmetrical arrangement of the skeleton. In external appearance it somewhat resembles a 

 Cladorhiza. In one of the specimens a great number of embryos (PL XLVI. fig. 7, e) 

 were found just beneath the surface of the sponge, lying, for the most part, between the 

 two sheaths of longitudinal fibres. 



As the dark brown colour of the specimens is shared by other things in the same bottle 

 it is possibly due to a discoloration of the spirit in whicli they were j^reserved; it 

 should be noted that the tissues, even to the centre of the sponge, are all diffusely 

 stained with the same rich chocolate tint. 



Carter's Esperia horassus (" Porcupine " collection) has an almost identical external 

 form, but our sponge stands alone in this resjject among its immediate congeners. 



The megasclera are large, but only about half as long as those of Esperiopsis profunda 

 (see below), and the species is further remarkable for having sigmata. 



Xoca/%.— Station 145a, December 27, 1873; lat. 46° 41' S., long. 38° 10' W.; off 

 Prince Edward Island ; depth, 310 fathoms ; bottom, volcanic sand. Three pieces. 



Esperiopsis edwardii, Bowerbank, sp., var. americana (PL XIX. figs. 7, 7', 7a). 



1866. Isodictya Edwardii, Bowerbank, Mon. Udt. Spong., vol. ii. p. 325 ; vol. iii., pi. IvLii. figs. 



15-18. 

 1866. (1) Isodictya paupera, Id., Op. cit., vol. ii. p. 328 ; vol. iii., jil. Iv. figs. 4-7. 

 1866. (?) Isodictya gracilis. Id., Op. cit, voL ii. p. 331 ; vol iii., pi. Iviii. figs. 23-26. 

 1880. Amphilectiis gracilis, Vosmaer, Notes Leyden Mus., vol ii. p. 111. 

 188.3. Amphilectiis Edwardi, Eidley, Journ. Linn. Soc. Lond. (ZooL), vol. xviL p. 106. 



Sponge massive, erect, in the form of a somewhat pyramidal column, 137 mm. in 

 height and about 44 mm. in diameter at the base ; based upon a stone, which is 

 encrusted with Polyzoa. Colour in spirit greyish-yellow. Texture rather soft and 

 spongy. Surface glabrous, but covered with low conuli. Dermal membrane distinct, 

 thin, transparent. Pores small, and scattered in irregular groups over the subdermal 

 cavities. Oscula not very numerous, scattered, about 3 mm. in diameter. 



Skeleton. — (a) Dermal ; the dermal membrane has no special skeleton ; the ends of 

 the primary fibres of the main skeleton abut against it, and it also contains a few 

 scattered stylote spicules, (b) Main ; this is rather diffuse and Halichondrioid, but with 

 distinct primary fibres running vertically towards the surface. 



