152 BRITISH PALAEOZOIC SPONGES. 



occurs, it has a conical head and simple rays directed backwards ; the shaft is 

 imperfect. This anchor is intermingled with acerate spicules similar to those 

 occurring with the zone-spicule. 



With the same forms of acerate spicules at Richmond, there are present one or 

 two examples of kidney-shaped spicules similar to those of the dermal layer of the 

 existing Geodia. They vary from '13 to *2 mm. in diameter. It is very doubtful 

 if these really belong to the same Sponge as the zone, anchor, and acerate spicules, 

 and they are but provisionally placed with them. These dermal spicules have not 

 previously been found so low as the Carboniferous Rocks. 



Distribution. — Yoredale series : Henblas, Trelogan, Flintshire ; Richmond, 

 Yorkshire. 



34. Geodites simplex, Hinde, sp. nov. Plate IV, fig. 3. 



1880. Aceeate spicule op unknown Sponge, Garter. Ann. and Mag. Nat. Hist., 



ser. 5, vol. vi, p. 212, 

 pi. xiv, fig. 15. 



Straight or curved acerate fusiform spicules, gradually tapering from the centre 

 to acutely pointed extremities. They vary from "55 to 1*4 mm. in length, and 

 about -1 mm. in thickness. No trifid or zone-spicules have as yet been found in 

 the same beds with these acerates ; but, judging by their form and proportions, it 

 seems probable that they belong to a Sponge of this genus, and they are provision- 

 ally included in it for convenience of reference. Some of the forms were obtained 

 by Mr. J. Wright from decayed chert, whilst others were found in a small hollow 

 in a block of chert. 



Distribution. — Carboniferous ; Upper Limestone series, Ben Bulben, Sligo. 

 Yoredale (?) series, Gwydfyd, Great Orme's Head, North Wales. 



Genus — Pachastrella, 0. Schmidt. 



1868. Die Spongien der Kiiste von Algier, p. 15. 



Syn. — Battersbya, Bowerbank ; Dercitus, Gray. 



Generic Characters. — Massive, nodose, platter-shaped, or irregularly expanded 

 Sponges, without specialised dermal layer, frequently attached to and incrusting 

 other Sponges. No special canals shown in fossil examples. The skeleton consists 



