THE SPONGES OF THE WEST-CENTRAL PACIFIC \7 



outline and distribution, the dermis is much thicker and continuous. The 

 pores are represented by numerous small openings about 30 /x in diameter 

 through these dermal membranes. The oscules are noteworthy and conspicu- 

 ous ; each is round, about 1 mm in diameter, and surrounded by a very dense 

 area devoid of pores, which area is about 4 or 5 mm in diameter and is raised 

 one or more mm above the surface of the sponge. Most remarkable of all, 

 these oscules are nearly as numerous on the outside of the sponge as they 

 are on the inside. Those which occur on the outside are even more conspicu- 

 ous than are those which occur on the inside. In the latter location they are 

 rather uniformly distributed, a little more than 1 cm apart, whereas on the 

 outside considerable areas are devoid of oscules, while in other places they 

 are less than 1 cm apart. 



The ectosome is uniformly characterized by foreign material, but over 

 the outside of the sponge it is scarcely more than 10 fi thick, and the debris 

 is very fine. On the inner surface of the sponge, instead of being uniformly 

 distributed, as it is on the outside, the cortexlike dermis is irregularly dis- 

 tributed. In places, even in the living sponge, it can scarcely be found, and 

 the subdermal canals are fully exposed. Yet on nearly half the interior 

 surface it is present, and upwards of 0.5 to 1 mm thick. These areas are 

 loaded with coarse foreign material. The endosome is crowded densely with 

 a fibrous reticulation. The flagellate chambers proved difficult to study be- 

 cause of the abundance of fibers, but they are certainly small and spherical. 



There are abundant ascending or principal fibers widely scattered 

 throughout the sponge, often about 150 /x in diameter and about 500 n apart. 

 These are loaded with foreign material. They are interconnected by even 

 more abundant secondary fibers, which are devoid of debris and are only 

 about 50 fi in diameter. These form meshes which are from 50 p. to 100 /j, 

 in diameter, rounded in outline, and which leave little space free from their 

 presence. 



This species is characterized chiefly by its shape. The abundance of 

 oscules on the exterior of the cone also is remarkable and is not equalled in 

 any other species in the genus. The nature of the fibers brings this species 

 into obvious relationship with some members of the genus Spongia, particu- 

 larly Spongia thienemannio (Arndt 1943, page 381). This is the Philippine 

 "Elephantear" sponge and is much like lekanis in most respects. The latter, 

 however, has the debris-filled dermis which characterizes the genus Phyllo- 

 spongia and, in comparison with Arndt's excellent illustrations, reveals sig- 

 nificant differences in the pattern made by the fibers. 



The species name is derived from a Greek word meaning "platter." 



