208 SUPPLEMENT. 



I have placed these fragments with some doubt under the genus Maplistion, for 

 the type of the genus, //. Armstrongi, Y. and Y.*, though possessing a fibrous 

 structure generally similar to these fragments, does not show any traces of spicules, 

 and its minute structure is therefore at present doubtful. Through the kindness of 

 Mr. John Young I have been able to examine a fragment of //. Annsfronr/i ; and its 

 fibres, indeiiendently of the absence of the spicules, appear to me to be of a more 

 robust character than those of the present species. 



Mr. H. J. Carter has also described a sponge from the same deposits under the 

 name oi Baphidistia vermiculata\, 'wh.ich. is probably allied to the present species. 

 Judging from the description and figures, R. vermicuJata is a fibrous sponge composed 

 of fusiform acerates of a sinuous form. Mr. Carter, however, regards the fibres as 

 belonging to a species oi Hydracthiia, awdi the sponge-spicules as parasitic on the 

 fibres. This view appears to me to be untenable ; and Mr. Carter himself suggests 

 that the fibres might probably belong to the sponge. The sinuous form of the 

 spicules distinguishes this species from //. fractum. 



Disfribution. Lower Carboniferous : Law Quarry, Dairy, Ayrshire. Collected by 

 Mr. James Bennie. 



Order TETRACTINELLID^, 6>. Schmidt. 



Genus GEODIA, Lamx. 



Geodia] antiqua, Hinde, n. sp. (Plate XXXVIII. figs. 5, 5 a-e.) 



Detached trifid spicules, with elongated cylindrical or subcylindrical shafts, from 

 ■2 to -.3 mm. in width, and with simple, short, obtusely-pointed head-rays, which 

 project upwards at an acute angle with the head of the shaft. The shafts are all 

 incomplete ; the longest preserved is 2 mm. in length, and it is of the same thick- 

 ness at the end as at the summit. Associated with the trifid spicules are curved 

 acerates of somewhat similar dimensions, which may probably belong to the same 

 species. The trifid spicules are distinguished by the relatively short and obtuse 

 head-rays and the regular thickness of the shafts. 



In the same deposit there are fragments of relatively large spicules, with robust 

 cylindrical shafts from -G to -9 mm. in thickness, and two short, stout, obtusely- 

 pointed opposite head-rays at the summit. The shafts are all incomplete ; the 

 longest fragment measures 3 mm. in length. These abnormal spicules may perhaps 

 pertain to a distinct species from the smaller forms. 



These spicules occur in the same beds of decayed chert of Carboniferous age which 



* Annals & Mag. Nat. Hist. ser. 4, vol. xx. p. 428, t. 15. f. 31-37. 

 t Annals & Mag. Nat. Hist. ser. 5, vol. i. p. 140, t. 0. f. 15-19. 



