166 BRITISH PALAEOZOIC SPONGES. 



so-called stellate spicules are all of small dimensions, they vary from - 3 to '67 mm. 

 in diameter. In some the primary six rays simply bifurcate, in others one or more 

 of the primary rays give off at their bases three or even four secondary rays, and 

 these may also subdivide. The smaller rays of these stellates seem to have all 

 originally possessed a spiral coil in the same manner as the larger, though it is now 

 scarcely perceptible. 



These various forms of spicules were met with quite detached from each other in 

 a bed of decayed chert, but there can hardly remain a doubt that they belonged to 

 the same species. The spicules are now of chalcedonic and crystalline silica, they 

 are of a creamy-white tint by reflected light, and translucent when examined in 

 Canada balsam. Only rarely can the axial canals be detected. I am indebted to 

 Mr. H. J. Carter, F.R.S., and to Mr. J. Wright, F.G.S., for the opportunity of 

 studying the type-specimens. 



Distribution. — Carboniferous Limestone: Upper series, Ben Bulben, near 

 Sligo, Ireland. 



Genus. — Aoanthaotinella, 1 Hinde, gen. nov. 



Syn. — Holasterella (in part), Hinde. 



Form of Sponge unknown ; the skeleton consists of relatively large spicules of 

 very varied and aberrant forms, but apparently modifications of the hexactinellid 

 type. In the simplest form there are only four rays in one plane at right angles to 

 each other, in others, five rays are present, whilst other forms possess six rays. 

 The rays may be straight or curved, sub-cylindrical or compressed. They fre- 

 quently bifurcate near their ends, and give off irregularly, spinous processes, so 

 that the extreme varieties are altogether abnormal in appearance. The spicules 

 frequently exhibit wide canals ; they are now of granular silica of a brownish tint. 



The spicules for which I propose this genus, differ very considerably in form 

 and structure from any other detached Sponge-remains mingled in the same 

 deposits with them. 



In many of them the number and arrangement of the rays appear to be in- 

 definite, and they do not exhibit any regular plan of structure. In others, however, 

 the primary rays are disposed like those of normal hexactinellid spicules ; but, owing 

 to the irregular development of spines and the subdivision of the rays themselves, 

 their typical character is largely masked. Further, their peculiar granular structure, 

 and the large and often hollow interior canals, contrast very greatly with those of 

 the other Sponge-spicules preserved with them under similar conditions, and seem 



1 aKarOa, a thorn ; clktIv, a raj, dimiu. 



