dredged up from the Gulf of Manaar. 137 



" euastrum rota" Sdt., which seems to be always quadri- 

 radiate with rays of equal length, viz. 12-6000ths, spined over 

 the outer half, and parting at the same angle from the centre 

 of union, where there is no body. But this spicule is confined 

 to the parenchymatous structure, of which there being none 

 or very little in the Manaar specimen from its thin, parasitic, 

 laminiform growth, may account for its absence there ; while 

 the same kind of smaller and more radiated stellates, about 

 half the size in both specimens, are equally abundant, in the 

 dermal layer especially. 



Besides Stelletta euastrum there are two other species with 

 discoid siliceous globules in the Adriatic, which Schmidt has 

 named respectively S. discophora and 8. mamillaris (Spong. 

 Adriat. Meeres, 1862, pp. 47, 48, Taf. iv. fig. 5, and Taf. v. 

 fig. 1, respectively), of which there is a specimen (for they both 

 appear to me to be the same species) in the British Museum, 

 obtained by Mr. Saville Kent from the coast of Portugal ; 

 and from this, together with Schmidt's illustrations, it is evi- 

 dent that the same kind of discophorous layer on the surface, 

 the absence of the zonular arrangement of the spiculation and 

 that of the " forks and anchors," so characteristic of Geodia, 

 exists in all, with a badly-developed condition of the zone- 

 spicule (which, as above stated, varies in the form of its head 

 from trifid to trifurcate, and in that of its shaft from long to 

 short, pointed and obtuse), scattered here and there amongst 

 the rest of the spicules without any apparent regularity what- 

 ever. In short, the structure is as different from that of a 

 Geodia as it is specifically characteristic of Pachymatisma 

 Johnstonia and Camimcs vulcan, Sdt. (op. et he. cit.). All of 

 these, therefore, although belonging to the Geodina, should 

 constitute a different group from Geodia proper. 



Stellettina. 



The chief difference between the Stellettina and Geodina is 

 the total absence of the " siliceous globule " in the former, 

 whether spheroid or discoid, leaving nothing but the " dermal 

 stellates " to rest upon the zone- spicules &c, which are for 

 the most part similarly arranged to those of Geodia, although 

 seldom with such characteristic regularity. 



Stelletta tethyopsis, n. sp. 

 (PI. VI. fig. 39 and 40 a-f.) 



General form subhemispherical and sessile, or spheroidal 

 and free (PI. VI. fig. 39). Colour grey. Surface uniformly 

 hispid from the projection of the forks and anchors, beneath 



