SILICIOUS AND HORNY SPONGES WILSON. 371 



mm. high, which conceals the aperture. No other apertures or spe- 

 cialized areas (see var. patellae-spinosae) are present. The sponge is 

 infested with the small brown actinian, so commonly present in this 

 species. The ectosomal anatomy and skeletal arrangement are as 

 in the type. 



Spicules. — 1. The oxeas are as in the type. 



2. (a). The large promonaenes of the radial bundles are perhaps 

 a trifle smaller than in the type. The clads measured were 180-300 ^ 

 long, sometimes irregularly wrinkled or bent, sometimes curved into 

 a hook-shape, sometimes with two bold curves like the horns of 

 certain cattle. 



The prodiaenes of the radial bundles are likewise somewhat 

 smaller than in the type. The clads measured were 90-180 |jl long, 

 sometimes unequal in length; often irregularly wrinkled or bent, 

 sometimes symmetrically so — that is, both clads bent alike. 



(b). The projecting protriaenes of the radial bundles are like 

 those of the type, perhaps in the average slenderer, the rhabdome 

 6-8 mm. long and about 24 p thick, the clads 50-100 \l long. These 

 are the chief elements of the surface fur. 



(c). The protriaenes of the fringes of the poriferous pits are 

 essentially as in the type. The rhabdome may be as thick as 28 [x, 

 the clads as long as 250 \l. 



The anatriaenes and sigmas are as in the type. 



Four other specimens smaller than the above were taken at the 

 same station. They range in shape from subspheroidal to hemi- 

 spheroidal or are even more flattened. They all have the flattened 

 basal surface so common in this species. They are all hirsute in 

 places, but have evidently been more or less rubbed. 



Holotijpe.— €at. No. 21308, U.S.N.M. 



TETILLA (CINACHYRELLA) CRUSTATA forma APERTA. new form. 



Station D5593, one specimen. 



The essential point of difference from the type lies in the presence 

 of unmistakable oscular canals which are easily distinguishable from 

 the poriferous pits. Whether this is a structural and fixed point of 

 difference between races, or whether it is a feature of physiological 

 anatomy (as, I think, it may turn out to be), one, that is, w T hich 

 varies with the physiological state of the individual, it is not pos- 

 sible to say. It is quite conceivable that in one and the same 

 poriferous pit the lining membrane may at certain times be per- 

 forated uniformly with many minute apertures, at other times with 

 fewer but larger ones, and that at still other times the apertures may 

 coalesce until all trace of a perforated lining membrane disappears, 

 the efferent canals then opening directly into the pit. This would 

 now be called a cloaca, or if one of the efferent canals happened to 



