HOLASTEEELLA. 153 



of spicules of similar form to the detached specimens, but with their rays amalgamated 

 together, so as to form an extended wall with stellate interspaces. The tubercles on 

 the upper or outer surfaces of the spicular arms ai'e much more developed than in 

 the detached forms, and the spicules themselves are more robust ; but the resem- 

 blance in form and the association of these fragments with the detached spicules 

 lead me to regard them as portions of the dermal layer of the same sponge. 



These umbrella-like spicules are rare in comparison with the simple hexactinellid 

 forms oi Hyalostelia Smithii occurring with them. A.t first sight they might be taken 

 to be merely abnormal varieties of the simple forms ; but the suggestion of Mr. Carter 

 that they probably belong to a distinct species, appears to me to be justified by the 

 combination of other irregularly-shaped spicules in Holasterella conferta. I have 

 named them in honour of Mr. John Young, F.G.S., of the Hunterian Museum, 

 Glasgow. 



Distribution. Lower Carboniferous : Cunningham Baidland, Law Quarry, Dairy, 

 Ayrshire. Collected by Mr. James Bennie. 



Holasterella Wrightii, Carter. (Plate XXXII. figs. 4-4 y.) 

 1880. Holasterella Wrightii, Carter, Ann. & Mag. Nat. Hist. vol. vi. p. 209, t. 14 B. f. 1-7. 



This species is based on detached spicules occurring in decayed chert from the 

 Carboniferous strata of Ireland. The spicules vary much in size and form, but they 

 are all apparently modifications of hexactinellid spicules. The simplest form is an 

 ordinary hexactinellid with three axes at right angles to each other. In other forms 

 one or more of the rays bifurcate, so that the extreme forms resemble small stars. 

 The spicular rays, both in the simple and complex varieties, are ornamented with 

 spiral rings. Rod-like spicules terminating in four recurved rays occur in the same 

 deposit, and may perhaps have formed the root-appendages of the sponge. 



Distribution. Lower Carboniferous : Ben Bulbul, Sligo, Ireland. Presented to the 

 Museum by Mr. Joseph Wright, F.G.S., of Belfast. 



Holasterella Benniei, Hinde, n. sp. (Plate XXXII. figs. 5-5 e.) 



1877. Incrusting Sponge ?, Young and Young, Ann. & Mag. Nat. Hist. vol. xx. p. 429, t. 15. 

 f. 41. 



Detached spicules of varied forms and relative large size. In the simplest variety 

 only five rays are present, four of which are horizontal and at right angles to each 

 other, and one vertical ; the rays are either simple or divided at their extremities. 

 In more complex varieties there are six primary rays, which are either simple or 

 divide and subdivide in an irregular manner, so that the extreme forms have a stellate 

 or a ramose appearance. The spicular axes vary from 2'5 to 4 mm. in length, and 

 from "5 to '9 mm. in width. 



X 



