NORTH AMERICAN PORIFER^. PART I. 405 



small and the vdiole resembles a honeycomb with small cells and walls of the finest lace.' 



The fibres are deficient in yellow filling. 



Nassau. Soc. Coll. 



Aplysina praetexta Ilyntt. 



The difference between this and the preceding species lies principally in the larger size of 

 the areas or honeycomb-like tubes inclosed by the net-like walls. These are so laro-e 

 and elongated that the honeycomb-like aspect of the surface of the skeleton is destroyed. 

 There is a similar Init very slight elongation of these openings near the outer edge in 

 Aj^Ii/sina gigantea, but in this species the honeycomb-like structure is only irregularly 

 maintained near the point of attachment on the inner side. The fibres themselves are 

 thinner, more delicate, and more elastic.^ The filling of yellowish matter occupies less of 

 the whole extent of the tubular interior of the fibres, which are black and empty to a much 

 greater depth than in Aplysina gigantea. The honeycomb-like openings have the same 

 structual character as in the preceding species, but both sides are much rougher and more 

 deeply indented in the dried specimen, owing to the greater 023enness of the supporting 

 skeleton. The form is similar to AjjJyshia, gigantea, which in all probability varies from 

 flabellate to cup-shaped, according to the surface upon which it grows. 



Nassau, 12 ft. on reef. Soc. Coll. 



Aplysina gigantea Hyatt. 



In this sjjecies the net work of the fibres in passing outwards, changes from an extremely 

 coarse and elongated mesh to a finer texture of attenuated and dark horny fibres destitute 

 of the yellow granular filling whicli gives a yellow tinge to the internal fibres.^ The honey- 

 comb-like tubes radiate from the centre outwardly, being shorter on the lower than on the 

 u^iper side of the specimens. The specimens examined were parts of a large cup-shaped 

 sponge with sides about eighteen inches broad, about ten inches deep in the centre, and 

 diameter unknown. It is described hy Dr. Palmer as a deep cup growing on the reefs, 

 attached in such a manner to the irregidar surface of the rock that the diver was only able 

 to detach the specimen in fragments. One of these shows the centre of the cup which is 

 hollowed out on the upper side. From this centre and from the other points of attachment 

 on the lower convex side large folds or irregular thickenings of the surface radiate toward 

 the circumference, the upper side being more plainly concave with fewer and more de- 

 pressed foldings. The lower side in the dried specimen is very cellular, owing to the falling 

 in of the external membrane, every cell being marked by a blind sac reaching nearly or 

 quite to the centre. The excurrent openings are, however, rare on the convex side, though 

 very numerous on the concave side. Portions of the convex side of this specimen exhibit the 

 condition described by Dr. Palmer in the living animal, when the dividing walls of the honey- 

 comb-like cells project shghtly above the external membrane, cutting up the surface into 

 polygonal figures in place of the deep cells described above. On the concave side those 

 portions of the surface which intervene between the numerous excurrent orifices maintain 

 nearly the aspect of the surface in the living sponge, while the orifices themselves have, in 

 most cases, been very much enlarged. The color, according to Dr. Palmer, is purplish black. 



Nassau, 12 feet on reef. Soc. Coll. 



IPI. 13, figs. 3, 4, 5, 6. SPI. 13, figs. 8-14. 



2 PI. 13, figs. 12-15. 



JIEMOIBS BOST. SOO. KAC. HIST. VOL. II. 102 



