136 Mr. H. J. Carter on Specimens 



in form, size, and position the most irregular of all. Size of 

 largest specimen, of which there are several, that of the group 

 of Siliquaria, about 2^ inches in its long diameter, com- 

 pressed. 



Hob. Marine. Parasitic on Siliquaria. 



Loc. Gulf of Manaar. 



Obs. This species was first named by Schmidt, who ob- 

 tained the specimen from Lacaze-Duthiers, who, again, got it 

 from La Calle, on the north coast of Africa, near Algiers 

 (Schmidt, Spong. Kuste v. Algier, 1868, p. 20) ; no descrip- 

 tion of it, however, is given beyond the spiculation, of which 

 I examined a mounted type specimen in the British Museum. 



The disk is, mutatis mutandis, identical with the siliceous 

 globule in development, structure, and location, while the im- 

 perfectly formed zone-spicule and its irregular location puts 

 one in mind of Pachymatisma Johnstonia (so abundant on our 

 coasts) ; still it appears to me to be more nearly allied to 

 Geodia than to Stelletta ; and therefore I have placed it, like 

 Pachymatisma, among my Geodina. Schmidt, as above 

 stated, has given it the generic name of " Stelletta" adding, 

 by way of designation, " euastrum." from the large and beau- 

 tiful form which some of the stellates attain in the specimen 

 from La Calle, but which do not occur in that of the Gulf of 

 Manaar — although they will be seen to do so in the Australian 

 form (fig. 42, c), which I will now describe, as it gives us 

 more of the internal structure than is to be found on the 

 laminiform growth over the group of Siliquaria (fig. 41). 



Stelletta euastrum, Sdt., S.W. Australian specimen, Free- 

 mantle. (PI. VII. fig. 42, a-c.) 



Ovular, now wrinkled from being dry ; 3 inches long by 

 \\ inch in diameter. Colour white externally — that is, the 

 colour of the petrous crust, — pale yellow internally, which is 

 the colour of the sarcode (PI. VII. fig. 42). Surface even, 

 dimpled, poriferous throughout (fig. 42, b b). Vents of diffe- 

 rent sizes scattered here and there (fig. 42, a a a). Dermal 

 layer composed of the disks before mentioned, mixed with 

 both forms of the flesh -spicule, about l-360th inch thick, 

 surrounding a pale yellow widely areolated body-structure 

 charged with the spicules of the species and, if anywhere, 

 less condensed in the centre than towards the circumference ; 

 thus, in the absence of any zonular arrangement and central 

 condensation like that of a typical Geodia, this species is 

 identical with Pachymatisma Johnstonia, Bk. Possessing 

 much the same kind of spiculation as the Manaar specimen, it 

 has, in addition, the large and beautiful stellate (fig. 42, c) 



