dredged up from the Gulf 'of ' Manaar '. 147 



cally unlimited. Again, it frequently happens that the dis- 

 cophorous layer has disappeared from some cause or other, 

 and that the surface is then formed by that condition of deve- 

 lopment where the disk has passed into a branched state, in 

 which the branches, curving over each other, leave interspaces 

 charged with the bacillar flesh-spicule (PI. VIII. fig. 48, a, 

 and 50 a, &c), which causes it to assume the appearance given 

 byDr. Bowerbank of his Dactylocalyx Prattii (Proc. Zool. Soc. 

 1869, pi. v. figs. 6-11), and the same in Theonella Sivin- 

 hoei, Gray (ib. 1868, p. 565), both of which specimens, now 

 in the British Museum, I have examined and find the disco- 

 phorous layer absent. Nor is this to be wondered at, from 

 what I have stated of the instability of this layer until the 

 disks have become transformed into the interlocking spicules ; 

 still there are no papillas on the spicules of Dactylocalyx 

 Prattii or of Theonella Swinhoei, which distinguishes them 

 from Discodermia papillata • but although the flesh-spicule is 

 elliptical elongate in Dactylocalyx Prattii, and bent in the middle 

 in Theonella Swinhoei, this is not sufficient for specific distinc- 

 tion between them ; nor is the flesh-spicule generally to 

 be depended on in this respect ; so, with this difference 

 only, I think, as Dr. Bowerbank has concluded (op. et I. cit.), 

 that Dactylocalyx Prattii and Theonella Swinhoei must be 

 considered the same species. Yet there is a large, vase-like 

 specimen to which I have before alluded, and which comes 

 from the seas about the Philippine Islands, in which the flesh- 

 spicules (for there are two forms) may be considered of some 

 specific value, since here the usual acerate curved micro- 

 spined and centrally inflated flesh-spicule is accompanied by 

 another equally plentiful, viz. a short thick ellipsoidal form 

 also microspined, not unlike the same kind of flesh-spicule in 

 Pachastrella abyssi,. Sdt. 



Discodermia aspera, n. sp. 

 (PI. VIII. fig. 49, a-i.) 



Surface even, discophorous, disks horizontal (PI. VIII. 

 fig. 49, a, b). Structure asperous, spinous, accompanied by 

 an acerate microspined flesh-spicule (PI. VIII. fig. 49, a, b) . 

 Colour grey. Discophorous structure and transformation 

 much the same as in the last-described species, only 

 that the margin of the disk soon becomes denticulated 

 (fig. 49, c), and the papillse pass into spines, as indicated 

 by the four gradationary diagrams (fig. 49, g) ; and in the 

 transformed disk (fig. 49,/) the irregularly lobed and den- 

 ticulated margin, together with the spines on the surface, 

 give that asperous appearance which more or less influ- 



