498. Transactions of the Society. 



Esperia faced by a crust of pin-like spicules arranged perpendicu- 

 larly to the surface of the Esperia, with their heads outwards and 

 their pointed ends struck into the dermal layer of the latter like 

 pins into a pin-cushion, so that these spicules appear to have been 

 appropriated by the Esperia itself, as I have before stated.* But 

 the fragment found by Dr. Millar not being more than one-third 

 of an inch in diameter, and very imperfect, does not afford sufficient 

 character for a description of the general form of the sponge, 

 although the details are quite enough to prove that it is what I 

 have stated. Herein, however, consists the most important part, 

 for the heads of the pin-like spicules and the anchorates respectively 

 are different in form from those of Bhaphidoiheca Mars! tall- Hallii 

 Kent, t Thus, the head of the former is flask-shaped elongate 

 (Plate XVIIa, Fig. 1), while that of K Marshall- Hallii (Fig. 2) is 

 globular oblate ; % and the small end of the inequianchorate com- 

 paratively longer and truncate (Fig. 3), not round and comparatively 

 shorter as in that of B. Marshall- Hallii (Fig. 4).§ In every other 

 respect B,. affinis is almost identical with B. Marshall-Hallii, as 

 slight differences in the size of spicules, such as may be found in 

 the larger bihamates of B. Marshall-Hallii, go for nothing in 

 specific distinction ; while the head of a pin-like spicule and the form 

 of an inequianchorate often vary much, even in the same individual. 

 Still, the differences in the form of the anchorate here seem to me 

 to be sufficient to constitute a variety, if not another species of 

 Esperia, and hence I have designated it " affinis " ; while the 

 difference in the heads of the pin-like spicules respectively, still 

 further strengthens this view. The pin-like spicule and anchorate of 

 B. Marshall-Hallii from a fragment of the type-specimen, are 

 figured in the Plate by the side of those of B. affinis for comparison. 



As, however, the form of the pin-like spicule both of B. Marshall- 

 Hallii and B. affinis, especially as regards its head, has, with 

 much search, not yet been found in any sponge possessing a pin- 

 like spicule, either as a Cliona about the specimen of Amphihelia, 

 or elsewhere, it becomes questionable whether the difference has 

 not been produced by the Esperia after these spicules had been 

 appropriated ; for the sarcode has the power of producing such 

 changes by the addition of more siliceous material in Sponges 

 where the spicules themselves have been produced. 



Still the value of Mr. Kent's record now becomes evident, for 

 what he has stated Dr. Millar has found to be repeated in another 

 species, and therefore it may fairly be inferred that other instances 

 of a like nature may follow. 



As regards the absence of the sinuous flesh-spicule in B. affinis, 

 while it is present in B. Marshall-Hallii, this does not militate 



* 'Ann. and Mag. Nat. Hist.,' 1878. vol. i. p. 170. 



t Ibid, 1870, vol. vi. pi. xv. J Ibid., /. c. fig. G. § Ibid, /. c. fig. 7. 



