GEODIA AMPHISTROXGYLA. 175 



antl efferents show that this sponge belongs to Geodia. Its nearest alhes appear 

 to be Geodia paupera Bowerbank, G. (Pachymatisma) inconspicua Bowerbank, 

 and G. (Cydonium) cooksoni Sollas. 



The locality of Geodia paupera is unknown and the locality given of G. 

 inconspicua, "South Seas" is hardly definite enough to be of value. Both these 

 species have smaller sterrasters, no mesoproclades, and no centrotyle amphioxes. 

 The choanosomal asters of G. paupera are strongj'lasters and not oxyasters as in 

 G. micropora, and the megascleres of G. inconspicua much larger than those of 

 G. micropora. I do not doubt, therefore, that these sponges are distinct from 

 Geodia micropora. 



I found it much more difficult to decide the question whether or not this 

 species is specifically identical with Geodia (Cydonium) cooksoni Sollas, which in 

 many respects resembles it and which also comes from the Galapagos (Charles 

 Island). The description given by Sollas ' is exceedingly meagre and unaccom- 

 panied by illustrations. I therefore asked my friend Mr. Ivirkpatrick of the 

 British Museum to send me a part of the tj'pe specimen of this species for exami- 

 nation and he had the kindness to accede to my request. I find that the sterr- 

 asters of G. cooksoni have nearly the same size, but are relatively thinner, than 

 those of G. micropora, and that the dimensions of the other spicules are 

 larger. This difference in size is particularly marked in the choanosomal asters, 

 the largest of which are in the tj'pe of Geodia {Cydonium) cooksoni fully twice 

 as large as the largest of G. minopora. It is for these reasons and also because 

 the mesoproclades have smaller clade-angles (average in G. micropora 51°, in G. 

 cooksoni 44°) and the large euasters relatively much larger centra in Geodia 

 (Cydonium) cooksoni than in G. micropora that I describe the latter as a new 

 species. 



Geodia amphistrongyla, sp. nov. 

 Plate 20, figs. 1-41. 



I establish this species for two fragments from Easter Island which may be 

 parts of the same specimen. Its choanosomal rhabds are not, as is the rule 

 in geodine sponges, chiefly amphioxes, but chiefly amphistrongyles, amphioxes 

 being absent altogether. To this remarkable peculiarity the name selected for 

 the species refers. 



Shape and .size. The larger fragment is an irregular, somewhat flattened 

 mass (Plate 20, fig. 31) 31 mm. long, 18 mm. broad, and 12 mm. thick. The 

 other, considerably smaller fragment is similar in shape. The surface is un- 



' Kept. voy. "Challenger," 1888, 25, p. 255, 256. 



