100 Mr. H. J. Carter on the 



project into the interspaces between the capsular spicules ; un- 

 accompanied by the spinous spicule, which is present in the 

 foregoing species, and without a continuous layer of the parnm- 

 liform spicule over the surface, but presenting one in contact 

 with the chitinous coat, where it is overlain by an extremely 

 thin development of the microcellular crust, from which the 

 lacinuliform processes above mentioned are projected. 



Loc. British Guiana {Schomburgk). British Museum, 

 general collection. Running no. 527. 



Obs. The most remarkable part about this species is the 

 cell-structure of the crust, which is just a transition in size 

 from that of Spongilla Carteri and 8. nitens to the minute 

 granular form of Parmula Batesii &c., thus showing that the 

 latter is also composed of minute cells, which, as before stated, 

 require a power of 450 diameters to be resolved. Thus with 

 Tuhella reticulata and Parmula Batesii we possess three of 

 those species with extremely rigid reticulated structure which 

 as yet have only been found in the river Amazons, but to which 

 the provisional genus '"'' Uruguay a^'' as will presently be seen, 

 also appears to be allied. 



Uruguaya, n. gen. prov. 



1. Uruguaya corallioides. (PI. VI. fig. 17.) 

 Spongilla corallioides, Bk., No. 20, p. 22, pi. xxxviii. fig. 13. 



Irregularly digitate ; rising into a polychotomous and 

 anastomosing mass of cylindrical branches, which may attain 

 several inches (7 or more) in all directions. Colour faint 

 whitish yellow or dark leaden on the surface, internally 

 white or colourless. (Surface even, vitreous in appearance, 

 extremely hard, smooth, and compact, interrupted by small 

 raised vents more or less uniformly distributed at short and 

 unequal distances from each other. Internal structure com- 

 posed of short densely reticulated fibre, formed of the skeleton- 

 spicules of the sponge in bundles firmly united together by 

 colourless sarcode, which, together with the spicules, in a 

 dried state simulates, from its hardness and vitreous appear- 

 ance, an entirely silicified mass. Skeleton-spicule very 

 robust, much curved, cylindrical, rounded at both ends, smooth 

 or microspined, about six times longer than it is broad. 

 (PL VI. fig. 17). Statoblast unknown. 



Loc. " Rapids " of the river Uruguay, above the town of 

 Salto, Uruguay. 



Ohs. This is a most interesting species in almost every 

 particular. 1st. Some of the specimens of it that have been 



