172 BRITISH PALEOZOIC SPONGES. 



which serve as notches, in which adjoining rays are held in position. In addition 

 to the normal-nmbrella spicules there are anomalous forms consisting of five or six 

 unequal rays diverging irregularly from a common centre. In these it is difficult 

 to recognise either the shaft or the transverse rays of the normal spicules. The 

 spicules are irregularly intermingled together, the smaller forms in the interspaces 

 between the larger. At their points of contact the rays are frequently firmly 

 fused together ; this fusion is evidently of natural origin, and not produced by 

 secondary fossilization. The connected skeleton is thus of an intricate, confused 

 character, in which it is not always easy to trace the individual spicules. 



In a large spicule a single ray is 4 - 6 mm. in length, and 1*3 mm. in thickness 

 at its base ; the rays of smaller forms are about 1 mm. in length. 



This species is based on a fragment of the connected skeleton, in which the 

 spicules retain their original arrangement, as well as on detached spicules. It is 

 characterised by the relatively large size and the irregular development of the 

 spicules. The dermal layer is not yet known. The form appears to be rare, and 

 limited in its distribution. 



Distribution. — Carboniferous. Lower part of Lower-Limestone series, Craw- 

 field Quarry, Beith, Ayrshire (J. Young). 



Genus. — Asteractinella. 1 — Einde, gen. nov. 



Syn. — Holasterella (in part), Carter, Hincle. Hyalonerna (in part), Young and 

 Young. 



Form of entire Sponge unknown, the skeleton consists of relatively large 

 spicules, in which a variable number of unequal rays radiate from a common centre 

 in different directions. The simplest form of these spicules has a principal vertical 

 axis, and from six to fourteen rays diverging from the centre at varying angles. 

 In another form one ray is conspicuously larger than the others, which radiate 

 star-like from its summit. In others the rays are subequal. The most complex 

 form consists of a number of rays extending from a common centre in a generally 

 horizontal direction; the proximal portion of these rays coalesces together, so that 

 the upper surface of the spicule has the appearance of the extended corolla of a 

 flower, whilst beneath this are three or four robust divergent rays (PL VIII, 

 figs. 3 e, Sf). Smaller spicules in which numerous simple blunt rays diverge from 

 a centre also probably belong to this genus. These various forms of spicules 

 appear to have been irregularly intermingled together to form the skeleton. A 

 few fragments have been found in which the rays of adjoining spicules are now 



1 doTi'ip, star j aKTiv t ray, diniin. 



