294 F. R. Coxoper Reed — Fossils from Girran. 



The plates decrease in size gradually downwards towards the base 

 or lower pole, but the specimen is very imperfect. However, the 

 distinction between the small convex, radially pitted plates with 

 depressed sutures on the upper surface, and these large, smooth, 

 almost flat, tile-like, overlapping plates of the lower surface, is most 

 marked, as Hinde has pointed out in R. occidentalis. 



As for the actual shape of this sponge from Woodland Point, the 

 evidence certainly suggests that the upper surface was domed ; the 

 base is imperfectly known, and whether it was concave like Ischadites 

 Konigi or convex or conical must remain at present an open question. 



No British species of Receptaculites appears to have been described 

 with the above characters, and the Scandinavian and Russian R. orhis, 

 Eichwald,^ from the Lower Silurian, appears to possess the nearest 

 affinities. 



The cast and impression of the specimen from the Middle Llandoveiy 

 of jSTewlands which has been entered in Mrs. Gray's list as Ischadites sp. 

 may probablj* belong to this same species. But it is in a poor state 

 of preservation, and consists of a mere fragment of the upper surface. 

 The plates are of regular rhomboidal shape, measuring about 2 mm. 

 along their longer diameter, and 1 mm. along their shorter diameter ; 

 their surface appears to be channelled and pitted, and pores are found 

 at their angles in the suture-lines, with 3-4 additional pores, usually 

 smaller iu size, along their sides. But the surface of the fossil is 

 much weathered and imperfect, so that it is difficult to know which of 

 these characters and structures are original. 



Receptaculites girvancnsis, sp. nov. (PI. XII, Figs. 3-6.) 



Shape crateriform, low, conical, with broad thick rounded lip and 

 obtusely pointed base. Plates very numerous, rhomboidal to quadrate, 

 all four sides being almost of the same length, very small near base, 

 increasing very gradually in size from base to lip of cup, arranged in 

 regular series of strongly curved intersecting rows in the usual ' engine- 

 turned ' fashion ; towards the lip the series run almost horizontally 

 owing to the strong curvature of the rows, and the plates of successive 

 series seem to lie in vertical rows. Lower plates near base sub- 

 quadrate, with surface flattened and overlapping slightly in tile-like 

 manner ; but becoming more and more convex towards lip, where no 

 imbrication is present, and a large pore lies in the grooves at each 

 angle between the plates. Surface of flattened lower lateral plates 

 smooth ; surface of convex lip plates ornamented with small irregular 

 pittings. 



Dimensions. — Diameter of cup, about 47 mm. ; height of ditto, 

 about 22 mm. ; size of plates on lip, 8 plates to every 10 mm. 



Remarks. — One large specimen, of which the dimensions are given 

 above, afi'ords 'the principal means of diagnosing the characters of this 

 form, but there is another smaller example broken off below the lip 

 which has a diameter of about 20-25 mm. and a height of 9-10 mm. 

 Both come from the Starfish Bed of Thraive Glen. The larger one 

 is fairly well preserved, though the surface of the plates is somewhat 



^ Rauff, op. cit. supra. 



