SPONGES.— HALLMANN. 



r^ 



n 



such as would suggest the term "honeycomb-hke," inasmuch 

 as Lendenfeld expressly uses this term, apparently in a dis- 

 tinctive way, in connection with another of his three species of 

 Plectispa (viz., P. macropora). To sum up, we may say that 

 the evidence is greatly in favour of the supposition that P. 

 arborea is a species of Echinoclathria, peculiar in the posses- 

 sion of a well-defined stem and in the 

 lack (owing probably to the manner of 

 arrangement of the trabeculae) of an 

 external appearance resembling that of 

 honeycomb. Since it is precisely in 

 these respects that the specimens of 

 Whitelegge's Echinoclathria elegans 

 are distinguished from the sponges of 

 the remaining known species of Echino- 

 clathria, it is without hesitation that I 

 here further describe them, with the 

 addition of figures, under the name of 

 E. arborea, Lendf. 



Description. — In its skeletal char- 

 acters generally, including the size and 

 form of the spicules, this species shows 

 no points of difTerence from E. ramosa. 

 Like the latter, also, it is invariably of 

 ramose habit ; but the branches are 

 relatively fewer and longer, and the 

 sponge, therefore, is arborescent — not 

 shrub-like. The essential differences 

 between the two species lie in the 

 character of the stalk and the form and 

 disposition of the trabeculje. 



The stalk is peculiar in the fact that it is structurally dif- 

 ferent from the branches — being almost or, sometimes, even 

 quite solid ; its condition in certain cases, however, indicates 

 that the non-trabecular structure is secondary. The foot of the 

 stalk usually spreads out into a disc of attachment : in the 

 specimen described by Lendenfeld, this would seem to have 

 been unusually large — "an extensive basal plate, slightly com- 

 pressed, and about 8mm. thick." 



The trabeculae of the branches are normally more or less 

 lamellar, but are relatively much stouter than in other species. 

 Occasionally, in parts of a specimen, or even throughout an 

 entire specimen, they are cylindrical, rod-shaped ; and, ac- 

 cordingly, in such cases, the structural character typical of 

 Echinoclathria is widely departed from. When the trabeculae 

 are lamellar, those which are situate at the surface of the 

 sponge are not disposed edgewise to the exterior, as in other 

 species, but are directed tangentially, and form wide 



Fig. 62>—E, arborea. 

 a Principal styles, b 

 Auxiliary strongyle. 



