Species o/" Uvnguaya, Cartey\ 3 



wood, and they appear as minute, brownish, wart-like bodies 

 from "5 to 2 millim. in width. These may consist of a single 

 gemmule or there may be a number, varying from two to 

 five, aggregated together in a single heap. Both the single 

 gemmules and the aggregated masses are enclosed by a layer 

 of spicules forming a kind of envelope or nidus, which com- 

 pletely invests them and conceals them from view. The 

 spicules of this investing layer are smooth and of the same 

 character as those of the sponge-skeleton, but distinctly 

 smaller, averaging '14 millim. in length by '018 millim. in 

 thickness. There does not seem to be any distinct arrange- 

 ment in the spicules of this layer ; in some cases, however, 

 they are side by side, in others crossing over each other irre- 

 gularly, and there is no aperture at its summit. Very fre- 

 quently this envelope is partially worn off, and the up]3er 

 portion of the gemmules is then exposed. The individual 

 gemmules are about '5 millim, in average diameter, very 

 sm.all forms are only "l millim., and a large example measures 

 •6 millim. across. Most of them are now partially collapsed 

 through desiccation ; but they appear originally to have been 

 subglobate in form. Their outer surfaces are smooth, and in 

 most of them no indications of an aperture can be seen ; in a 

 few there are one or more slightly raised s]:)ots in a lateral 

 position, which may represent apertures. The gemmule is 

 furnished with a single layer of amphidisc-spicules, very 

 regularly and closely arranged, so that the outer surface has 

 the appearance of being studded over with microscopic nail- 

 heads. These amphidiscs are very regular in size, averaging 

 •016 millim. in height and the same in the width of the 

 rotules. The shafts are cylindrical, and they project beyond 

 the rotules at both ends in the form of bluntly rounded pro- 

 cesses. I'he rotules are approximately circular in outline, 

 with smooth, complete, curved, saucer-like margins, which 

 are invariably turned in the same direction. 



This species differs from U. coraUioides^ Bowbk., sp., in its 

 incrusting mode of growth, in the absence of definite oscules, 

 in the smaller dimensions of the skeleton-spicules, and in the 

 presence of gemmules. From the incrusting species of Uru- 

 guay a or Potamohins, described by Dr. W. Marshall* from 

 the Congo, the present form differs in the absence of definite 

 oscules and in the slighter proportions of the skeleton-spicules, 

 likewise in the presence of gemmules, which have not yet 

 been met with in any of the Congo forms of the genus. 



* Zeitsclirift fur Naturwissenscliaften, N. F. Bd. ix. pp. 553-577. 

 See also a translation of this paper in Ann. & Mag. Nat. Hist. ser. 5, 

 \ol. xii. (.1883), pp. 391 -412. 



