236 DR. niNDE AND MR. HOLMES OK SPOIS^GE-REMAIXS 



of recent species of Geodia. It is probable that the differences 

 in size and form may indicate different species. Fig. 32 a repre- 

 sents a portion of the surface of a globate, showing the spined 

 heads of the extremely fine acuate spicules of which, it is 

 composed. 



Discoidal Spicules q/Erylus, Gray. 



Erylus (a). — PL XIV. fig. 33. Discoidal spicules, elliptical in 

 outline, consisting of an aggregate of hair-like spicules, the 

 summits of which project sliglitly as small spines. These spicules 

 vary considerably in size: a small specimen is 'llS mm. in length 

 by '076 mm. in width ; whilst a large form, like that figured, is 

 •175 mm. by '122 mm. x\s a rule these spicules are larger than 

 those of the recent JEryJus {Stelletta) mamillaris, Osc. Sch., sp., 

 the type of the genus. As fossil these spicules only appear to 

 have been hitherto noticed in the Tertiary radiolarian beds of 

 Barbados, by Mrs. Bury (' Figures of remarkable forms of 

 Polycystines in the Barbados Chalk Deposit,' 1862, pi. xxiii. 

 fig. 2). Detached recent spicules are plentiful in dredgings from 

 off the S.W. coast of Australia in depths of 3000 fathoms. 



Erylus (b). — PI. XIV. fig. 34. Extremely thin, circular or 

 elliptical, plane or plano-concave discs or plates, consisting of an 

 aggregate of delicate acuate spicules radiating from a centre. 

 Their surfiices are minutely tuberculate, and their summits 

 rounded. Length '125 mm., width "105 mm. These spicules are 

 of the same character as the dermal spicules of Erylus {Stelletta) 

 euastrum, Osc. Sch. (Algier. Spong. 3rd Supp. p. 20, pi. iv. figs. 

 4 a, h, c, d), from ofi' the coast of Algiers. 



Dermal Spicules of unknown Spooige (Dactylocalycites, Carter', 

 Placolithis, pars, Ehrenherg). 



PI. XIV. figs. 35, 36, 37. Thin siliceous plates, circular, 

 elliptical or suboblong in outline, with a series of flask-shaped, 

 round or elongate perforations just within the margin and a vary- 

 ing number of fine canals either extending across the spicule or 

 radiating from the centre. These canals terminate just within 

 the spicular margin in the spaces between the flask-shaped per- 

 forations. They vary in number : in a small specimen (fig. 37) 

 there are only three, which extend across the plate, but do 

 not appear to interconnect where they cross each other ; in 

 larger forms there are from 9 to 18 canals, which appear to 



