NORTH AilERICAN PORIFER^. PART II. 533 



SroiSTGELIA Ndo. 



Dysidea (pars) Johnson. 



Spongionella Bow. 



Caccospongia (pars) Schmidt. 



This genus is readily distinguished from Spongia in the dried specimens of most of the 

 species by the character of the surface. It is made up of contiguous, sunlven, angulated 

 areas, giving the surface a celkdar aspect, \i\Le that of a cut honeycomb. The cells are 

 not deep, and are formed solely by the shrinkage of the outer membrane over the project- 

 ing points of the primary fibres. These are large, radiatory and single ; the connecting 

 tissue of secondary fibres is also characteristically regular in most species, and has a 

 large, loose mesh, with the fibres at right angles with the primary fibres. The surface is 

 covered by the projecting primary fibres, and as these are single they give a fine woolly 

 aspect to the otherwise even surface of the skeleton, quite distinct from that of some sjdc- 

 cies of Spongia, or of any other genus. The secondary fibres are clear, and the jjrimary 

 fibres usually, though not in all cases, loaded with foreign matter. Quite a number of 

 the species show exceptional characteristics, but all of them appear to have the character- 

 istic singleness of the primary fibres. Several sjaecies show the peculiar modification de- 

 scribed by Schmidt as a distinct genus, Ditelia. In one species, Spongelia velata, the sur- 

 face is so completely changed in this respect that I am not entirely convinced that it may 

 not .some day justify a new generic group. There is no doubt, however, that what was 

 described first as Ditelia was only a common variation liable to occur in any species of 

 either Spongia or Spongelia, as was subsequently shown by Schmidt himself.^ The figure 

 of Spongionella pulchella Bow., appears to show that this species is a true Spongelian, and 

 the microscopical figure of the fibres and the written description, are very characteristic of 

 Spongelia. 



Spongelia incerta Hyatt. 



I presume that no one would suspect this specimen (PI. xvi, fig. 32) of being anything 

 but a pedicellated form of the true genus Spongia. The surface is smoother even than in 

 Spongelia densa, the mesh of the fibres very small, and the fibres themselves, like the finest 

 of the Spongiae, are very elastic and closely woven. I did not suspect the real affinities of 

 this interesting form until a section was made, when the comparatively large j^rimary 

 fibres loaded with foreign matter, and the character of the connecting tissue, became visible. 

 The spaces are filled by the finest fibres forming a close cellular network, much more regu- 

 lar in the form of the mesh than is common among the true Spongije. In some parts where 

 the primary fibres approximate, the secondary fibres here and there stretch across, forming 

 the usual ladder-like tissue. The form is flabellate, but very thick in proportion in the 

 centre, so that when seen from above one side is ver}' gibbous. The pedicle is long and 

 rather small, but with the usual dense hard texture of the pedicellated forms of Spongelia. 

 The excurrent orifices are scattered, but the majority occupy the outer edge. The incur- 

 rent orifices are very numerous, regularly distributed over the entire surfiice, and can be 

 plainly seen in the skeleton as round holes. The surfiice is otherwise perfectly smooth. 



Loc, Phillips Island, Australia, in Soc. Coll. 



1 Spongien d. Adriat. Meeres, 18G2, and Suppl., 1864. 



UEMOIBS BOST. SOC. KA-T. HIST. VOL. U. 134 



