352 SILICEOUS SPONGES. 



rays are straight or slightly curved. The spicules vary from '45 to 1-05 mm. in 

 length. 



Distribution. Upper Chalk : Horstead, Norfolk. 



Genus HOLASTERELLA, Carter, 1879. 



HoLASTEKELLA coNFEETA, Carter. (Plate XXXII. figs. 2-2/.) 



1879. Holasterella conferta, Carter, Ann. & Mag. Nat. Hist. ser. 5, vol. iii. p. 141, t. 21. 

 f. 1-8. 



1877. Hyalonema Sinithii, Young and Young, pars, Ann. & Mag. Nat. Hist. vol. xs. p. 426, 

 t. 14. f. 20, 21, 22. 



1878. Hyalonema Smithii, Carter, pars, Ann. & Mag. Nat. Hist. vol. i. p. 129, t. 9. f. 11 a-e. 



Sponge club-shaped, composed of abnormal varieties of hexactinellid spicules. The 

 simplest form is a spicule with five arms or rays at right angles to each other, and 

 the sixth ray at the summit of the vertical axis is replaced by several minute upright 

 or radiating processes. In more complex forms these processes at the summit are 

 elongated, and occasionally bifurcate so as to form a group of radiating rays, which, 

 in some cases, are sufficiently numerous to give the spicule a star-like form. The 

 most abnormal variety is a spicule with a flattened or platter-shaped summit composed 

 of numerous (18 to 25) fusiform, smooth, or tubercled rays, united laterally so as to 

 resemble the petals of a flower. The summit is suj^ported on three or five smooth 

 rays which spring from its under surface. Mr. Carter does not appear to have met 

 with this variety ; but in the collection made by Mr. Bennie it occurs in situ, 

 associated with the simpler spicules of this species, and it is not improbable that it 

 may have been a modified surface-spicule. There is a great variety in the dimensions 

 of the spicules of this species ; the rays vary from '5 to 2-5 mm. in length. 



Distribution. Lower Carboniferous : Law Quarry, near Dairy, Ayrshire. Collected 

 by Mr. James Bennie of Edinburgh. 



Holasterella Youngi, Hinde, n. sp. (Plate XXXII. figs. 3-3 d.) 



1877. Stellate Spicules, Young and Young, Ann. & Mag. Nat. Hist. ser. 4, vol. xx. p. 420, 

 t. 14. f. 13, 19, 23, 24, 27, 29. 



1878. Hyalonema Smithii?, pars, Carter, Ann. & Mag. Nat. Hist. ser. 5, vol. i. p. 129, t. 9. 

 f. 10 a, b. 



I propose this species to include detached spicules consisting of five to seven com- 

 pressed, straight, or slightly incurved, horizontally extended rays, springing from a 

 common expanded centre, with a single vertical ray beneath. The upper surface of 

 these umbrella-shaped spicules is either smooth or tuberculated. The spicular rays 

 vary from "4 to 2 mm. in length, and from •07 to '7 mm. in width. In the same beds 

 with these detached spicules there are flattened fragments of spicular mesh composed 



