MERRILL : FOSSIL SPONGE SPICULES. 17 



Figure 19. Hymeraphia 1 sp. Outline perfect. Body egg-shaped, 

 and saccular. Spines irregularly arranged on body, short and perhaps 

 divided at tip. Size : 0.042 mm. by 0.037 mm. ; length of spine, 

 0.0057 mm. Somewhat similar forms are figured by Carter as belonging 

 to the recent genus Hymeraphia. 1 It is therefore placed provisionally 

 in this genus. 



Figure 20. Geodia? spinipansata, n. sp. Outline perfect. Body 

 egg-shaped and ornamented in a most peculiar way. The significance 

 of the two apparent openings on top is not understood. Spines irreg- 

 ular in length and size, and variously divided at the terminations. Size : 

 diameter, 0.092 mm. ; average length of spine, 0.0307 mm. This pecu- 

 liar form was not found figured, but from its spiny form I placed it with 

 Geodia, and suggest the specific name spinipansata. 



Figure 21. Geodia? HUH, n. sp. Spicule perfect. Body elongated 

 and smooth between bases of spines. Spines few and irregularly placed, 

 spreading at base, tapering rapidly at first, then more slowly to the top 

 from which extend three to five short barbs. The hollow tube may be 

 seen the whole length of the spine. Size : 0.0938 mm. by 0.0884 mm. • 

 length of spine, 0.0307 mm. This species is one of transcendent beauty. 

 Nothing similar has been found figured. It perhaps belongs to some 

 genus allied to Geodia, and I propose the specific name HUH. 



Figures 24, 25, 26, and 30 are very small globo-stellates covered thickly 

 with small straight short spines. They vary in size from 0.023 mm. 

 by 0.021 mm. to 0.028 mm. by 0.015 mm. Similar figures have been 

 figured by Carter, 2 in describing the recent form Hymeraphia spiniglobata. 



Figure 27. Small, circular, flat silicious disks with a smooth surface 

 and often a dark somewhat irregularly shaped mass in or near the centre. 

 Some of these having a dark spot in centre appear to have been replaced 

 by amorphous silica, and the dark spot may be a collection of organic 

 residue, though Sollas found that a dark spot in the middle of a recent 

 sponge spicule was an air bubble. This form is very common, and often 

 a hundred or more are found piled upon each other like piles of coin. 

 Some of them are solid, but the greater number have a ring around the 

 centre, or a black spot filling the centre. They also vary greatly in size ; 

 the ones figured are an average ; diameter, 0.05 mm. 



Figure 28. Dermal spicules'? Rhomboidal and apparently flat in 

 shape. Surfaces often pitted. Average size, 0.021 mm. by 0.0307 mm. 

 Not found figured. 



i Ann. Mag. Nat. Hist, Ser. 5, 1879, Vol. III. Plate XXVI. 

 3 Ibid., Vol. III., p. 301, PL XXVI. Figs. 5-16. 



VOL. XXVIII. — NO. 1. 2 



