SPONGES.-HALLMANN. 



289 



but by auxiliary ; and as the remaining species are very ana- 

 logous to E. glabra and E. reticulata in point of spiculation, it 

 is extremely probable that in their case also, the axial spicules 

 of the fibres are auxiliary. The supposed resemblance between 

 Echinochalina and Echmodictyuni is therefore a fictitious one, 

 since in the latter genus it is unquestionably the principal 

 spicules which core the fibres. 



Echinochalina reticulata, Whitelegge. 

 (PI. XXX., fig. 2, and fig. 66.) 



Sponge of rounded massive form, consisting of a honey- 

 comb-like reticulation of very thin, almost membranous, 

 lamellce ; the superficial lamellce, as a ride, present their 

 edges to the extenor. Superficial ''cell-apertures"' 

 averaging about 8 mm. in diameter. Skeleton (of each 

 lamella) an irregular ''bi-dimensional" reticulation of 

 main and connecting fibres. Main fibres zvitli a sparse 

 core of slender cylindrical (auxiliary) mcgascleres varying 

 in form from tornotely-pointed subtylostyli to amphisiron- 

 gyla; connecting fibres vacant: all the fibres abundantly 

 echinated by principal styli, conical in shape except for a 

 slight sub-basal constriction. Auxiliary megascleres arc 

 abundantly scattered between the fibres. Megascleres, 

 sizes of: — (/.) Principal styli, length 120 to I'/O p., maxi- 

 mum diameter 10 p; (ii.) auxiliary spicules, length 180 to 

 2JO yi, maximum diameter 4 y.. Microscieres absent. 



An examination of the single specimen (the type-specimen, 

 preserved in a dry state) which I have seen of this species, 

 provides nothing of importance that might be added to the 

 original description, except as regards the auxiliary megas- 

 cleres. These — which are cylindrical, more or less basally 

 expanded (i.e., subtylote), monactinal spicules — are usually 

 tornotely pointed ; but in a small proportion of them — between 

 which and the preceding are many individuals of intermediate 

 character — the distal extremity is rounded off like the end of 

 a strongyle. I am unable to support Whitelegge in his 

 statement that these strongylotely-ended spicules, which he 

 erroneously terms tylota, occur chiefly in the dermal layer ; 

 rather does it appear to me that they are intermingled with 

 the others promiscuously. 



In agreement with the thin membranous character of the 

 lamellse, the reticulation of fibres which forms the supporting 

 skeleton of anv given lamella extends only in two dimensions 

 or, in other words, all the fibres composing it are parallel to 

 the plane of the lamella. 



As the original figure does not convey a sufficiently clear 

 idea of the appearance of the sponge, a further figure on a 



