﻿SPONGES. -KALLMANN. , - j 



largest measure about jjo x 4 /<. Beneath the surface of the 

 sponge and running perpendicularly towards it are numerous 

 wispy strands of the same spicules. With regard to the ar- 

 rangement of the skeleton Microciona scabida stands precisely 

 in the same relation to the type-species of Stylotellopsis — 5. 

 aniahilis'^ — as does Crella incrustans var. levis to C. incrustans 

 var. piimila; and, in compliance with the present scheme of 

 classification, should accordingly be placed in Thiele's genus. 



Another interesting species whose systematic position ap- 

 pears to be somewhere in the vicinity of Clathrissa and Stylo- 

 tellopsis is Echiuodictyiim ridleyi, Dendy.2 The skeleton is 

 made up almost entirely of slender longitudinal wispy fibres 

 and is consequently rather of the dendritic than of the reticu- 

 late type. Accompan\ing the slender oxeote or rather torno- 

 toxeote spicules (size about 270 x 4J1) which chiefly compose 

 these fibres, are a few conical smooth styli (190 x 7 ;i) and 

 acanthostyles (100 x 6;^), both kinds of which occasionally 

 project from the fibres somewhat in the manner of echinating 

 spicules. There are no microscleres. The diactinal spicules 

 of the fibres evidently correspond to the auxiliary megascleres 

 of normal Myxillinse, and the species accordingly possesses 

 no claim to a place in the genus Echinodictyuni in which the 

 fibres are formed by principal spicules and in which the aux- 

 iliary spicules are represented by interstitial or dermal styli. 

 Also, it is scarcely to be doubted that the smooth conical styli 

 are homologues of the larger acanthostyles of Clathrissa 

 arhiiscula, Stylotellopsis amahilis and 5. (Microciona) scabida 

 and to the principal styli of normal Myxillina?. C. arbuscida 

 and .S'. amahilis differ in generic characters mainly in this 

 respect, that in the latter the auxiliary megascleres are pointed 

 at one end only, whilst in the former they are pointed at both 

 ends. But this difference cannot be regarded as of much im- 

 portance since the probability is that the tornotoxea of C. 

 arbuscida are, strictly speaking, just as truly monactinal as 

 the tornostrongyles of S. amahilis. Consequently Echino- 

 dictvum ridleyi owing to the perfect smoothness of its prin- 

 cipal styli, stands farther removed from either of the two last 

 mentioned species than these do from each other, and is thus 

 fairlv entitled to distinction under a new generic name. In 

 E. ridleyi, as already mentioned, the principal and accessory 

 stvli are both comparatively rare in their occurrence ; if the 

 former spicules were to disappear, such a species as Echino- 

 dictvufn spongiosum, Dendy,^ would result; whilst if both 

 kinds were lost, there would be scarcelv anvthing in the struc- 



1 Thiele -Fauna Chilensis, Bd. 3, p. 456, fig. 72 a-d. 



2 Dendy—Proc. Eoy. Soc. Vict., viii., 1896, p. 44. 



3 Dendy—Proc. Eoy. Soc. Vict., viii., 1896 p. 45. 



