SILICIOUS AND HORNY SPONGES WILSON. 403 



the variety. The fistular processes are either represented by merid- 

 ional ribs or are very flattened and arranged in meridional rows. 

 The spicules measure 400 by 20 jx, and are, as in the preceding, round- 

 pointed oxeas — that is, rounded off at the apex. Sharp-pointed 

 smaller sizes of the spicule occur. 



Holotype.— Cat. 21285, U.S.N.M. 



The Albatross specimens of type and variety make a series that is 

 veiw suggestive for the study of the origin and nature of variations. 

 But how far the differences are phaenotypic and how far due to 

 racial differences remains to be ascertained. 



The laminated condition of the skeleton which I have described is 

 something not peculiar to P. testudinaria, for Hentschel has de- 

 scribed in two other forms, P. truncata aruensis and P. nigricans 

 irregularis (1912, pp. 402, 405), a concentric arrangement which is 

 somewhat similar. Perhaps such lamellae are to be looked on, in 

 part, as Hentschel suggests, as representing growth rings, but it 

 would seem that they constitute, at least in P. testudinaria, an estab- 

 lished, constant feature of the skeletal arrangement. 



The laminated structure of the skeleton in these species of Petrosia 

 and in Coelosphaera toxifera of this report probably only constitutes 

 a case of analogical resemblance. Petrosia is probably however a 

 near relative of the Phloeodictylnae (see Lundbeck, 1902, p. 56 ; 1910 

 p. 28), and a form like Petrosia testudinaria, var. flstulophora consti- 

 tutes, at least in the matter of morphological plan, an intermediate, 

 showing how a vase-shaped Petrosia through continued increase in 

 thickness of wall and decrease in size of the cavity, coupled with the 

 localized outgrowth of surface projections, might pass into a massive, 

 fistulate, phloeodictyine sponge. 



PETROSIA LIGNOSA, new species. 



Plate 41, fig. 3 ; plate 48, fig. 9. 



Two dried specimens from stations D5147 and D5250. The speci- 

 men from D5147 (pi. 41, fig. 3) represents about one-third of a great 

 conical vase with small truncated solid base (vase was sawn in two 

 when collected). Total height of vase about 600 mm.; diameter of 

 mouth of vase about the same; wall in general 50-75 mm. thick. 

 The sponge from D5250 is a vase 400 mm. high ; cross diameters of 

 mouth 300 mm. and 500 mm. ; thickness of wall 110 to 150 mm. In 

 both, the outer surface is closely beset with large, gnarled protuber- 

 ances disposed without any definite arrangement. Between many of 

 these and also on them are abundant, small, mammillate (subcorneal 

 or subcylindrical) projections, rounded apically, 5 to 15 mm. high 

 with a width something less than the height. Inner surface of vase 

 smooth. Canals, up to 5-6 mm. in diameter, extend in radially from 

 both surfaces, their mouths covered over by dermal skeletal reticula. 



