328 ON AN APHEOCALLTSTES FROM THE DEEP SEA.. 



and insufficient diagnosis of CyatJiella lutea suffices to dis- 

 tinguish one from the other (Schmidt, op. cit. p. 46, Taf. vii. 

 fig. 2). 



A still greater resemblance in shape exists between the new 

 form and Rhabdodictyon delicatum, Schmidt {op. cit. p. 46, Taf. vii. 

 fig. 3); but the beautiful rosette of this very lax-meshed Mexican- 

 sea species is not distinctive. The rest of Schmidt's diagnosis is 

 insufficient to establish a species. 



On the seventh plate of the same work, Schmidt gives some 

 figures of Aphrocallistes Bocagei ; and one is interesting (fig. 5 B), 

 for it indicates a young specimen with its base. It is, as far as its 

 lower third is concerned, very much of the size, and resembles in 

 shape, the new form ; but there are no indications of the peculiar 

 basal structure just described. 



Finally, there are some points of resemblance, but not sufficient 

 to necessitate a generic alliance, with Aulodictyon, S. Kent. 



DESCRIPTION OF THE PLATES. 

 Plate XXIV. 



The Lithistid sponge. 



Fig. 1. The body, natural size. 



2. A transverse section, natural size. 

 2 a. The same, magnified. 



3. Large column-spicula of the radial open structure, magnified. 



4. A spicule of the concentric close structure, magnified. 



5. Smaller spicula from the same region, magnified. 



6. Spicula with spinuled limbs, magnified. 



7. Spinules, magnified, of preceding fig. 6. 



8. Contact spicula, with minute spinulose junctions, magnified. 



9. The spicula just within the cortex, magnified. 



10. Peltate cortex, dendritic, modified trifid spicula, magnified. 



Plate XXV 



Aphrocallistes sp. 



Fig. 1. The specimen, natural size. 



2. Large common derm-spicula, magnified. 



3. Hexactinellids with long axis more or less ragged, magnified. 



4. 5. Minute hexactinellids, magnified. 



6. A multidentate scopuline, magnified. 



7, 8. Brush -spicula, magnified. 

 9. Rosette, magnified. 



10. An incomplete xosette, with a long axial fibre, magnified. 



11. Rosettes, trifid, magnified. 



