84 



Eyalonema heideri F. E. Sch. 

 Plate II, fig. 15-22. 



1895 Byalonema heideri P. E. Sch. in Abh. Prenss. Ak. 189-1, p. 23, Taf. Ill, figa. 15-22. 



Togetlier with the Hyalonema aculeatum, characterised by the long, protrud- 

 ing prostalia lateralia, a pear- or turnip-shaped sponge, similar in shape and of 

 equal size, 10 mm. high and 5 mm. broad, was found, which however is entirely 

 destitute of the prostalia lateralia and quite smooth (pi. II, f. 15). 



Having cut this specimen into a continuous series of longitudinal sections, 

 500 H- thick, I could easily see that it resembles Hijalonema aculeatum also in the 

 shape, size and position of all the spicules, most of which are represented in fig. 

 16-22 on plate II. I only noticed that the dermal macramphidiscs are consider- 

 ably larger, about 300 m long (pi. II, f. 20). 



I must confess I was long in doubt whether I should consider this sponge 

 as a smooth variety of Hyalonema aculeatum or as a distinct species. I have 

 followed the latter course provisionally, because it seems unlikely that such 

 a great difference as is expressed by the presence of large prostalia lateralia in 

 one, and their absence in the other, should have no specific value. But it must 

 be acknowledged that we are hardly yet in a position to pronounce a final judg- 

 ment on the systematic value of differences such as these in the Hyalonema- 

 tidx. 



I have named this species after my friend and collaborator Prof. Carl 

 Heider, with whom I have had occasion to discuss scientific questions like the 

 one involved here, very frequently. 



The only specimen of this species was found, together with the nearly allied 

 'Hyalonema aculeatum, near North Sentinel Island in the Andamans in a depth of 

 458 m.==:250 fths. 



Hyalonema jyirum ¥ . E. Sch. 

 Plate II, fig. 23-30. 



1895 Hyalonema pirum F. E. Sch. in Abh, Preuss. Ak. 1894, p. 27, Taf. Ill, figs. 23-30. 



Although it seems to me doubtful whether the small Hyalonema specimens 

 from the Andamans (pi. II, f. 23-25) here described as Hyalonema, pirum, really 

 represent a distinct species, or whether they are merely young forms of Hyalonema 

 indicum or some other Hyalonema, I consider it for the present better to give to 

 these sponges, distinguished as they are by certain peculiarities from all other 

 known Hyalonemas, a separate name, than to place them arbitrarily in some 

 other known species of which they may possibly, but do by no means certainly. 



