174 THE VOYAGE OF H.M.S. CHALLENGER. 



the lattei- is either conically pointed as above (PL LXIX. fig. 5), or becomes gradually 

 narrower towards the end. 



In the fibrous rudiment of a stalk, the majority of the long diacts, which vaiy ex- 

 ceedingly in thickness, have their ends thickened in club-like fashion, or thickly beset 

 with spines, while on the surface of many which are otherwise smooth small spines occur 

 on the middle portion. Towards the lower end of several of the long diacts, which 

 are disposed in longitudinal bundles parallel to one another, one finds spines, bosses, or 

 protuberances of some kind projecting laterally. These seem to represent the rudi- 

 mentary traces of the synapticula which are subsequently seen in their developed 

 form. 



The radially disposed, freely projecting prostalia, which are found on the side and 

 probably were also on the superior margin of the cup-shaped body, are oxydiacts measuring 

 2 to 4 cm. in length. Their freely projecting surface is, for the most part, somewhat 

 thickly studded with numerous minute, quite irregularly scattered, conical bosses or 

 spines. 



Genus 10. Aidocalyx, n. gen. 

 This genus contains only one species, Aidocalyx irregularis. 



Aulocalyx irregularis, n. sp. (PL LX.). 



OS" Marion Island, south-east of the Cape of Good Hope (Station 145a, lat. 

 46° 41' S., long. 38° 10' E.), from a depth of 310 fathoms and a volcanic sand bottom, 

 several much injured and partially macerated specimens of a Hexactinellid were dredged. 

 The lattice framework still hung together, and the general form was that of a broadly ex- 

 panded cup with complex, much folded or diverticulated wall (PL LX. fig. 1), similar to 

 that observed in Periphragella elisae, Marshall. Although the fragments obtained were 

 only from 3 to 4 cm. in height, it seems probable that the uninjured cup was at least 

 twice as high. Of the soft tissue only some very small fragments remained. 



The skeletal framework, which is moderately thick at the base and as hard as stone, 

 becomes gradually looser and more delicate towards the upper end, and finally so sparse 

 and thin, that, as in Regadrella, Dictyocalyx, Rhahdocalyptus, Hertioigia, &c., one is 

 inclined to believe that in the upper, most recently added portion no firm fusion of the 

 skeletal elements has occurred. 



As to the general structure of the soft tissue, it must be noted that between the two 

 sieve -like, perforated, bounding lamellae of the body-wall (the dermal and gastral mem- 

 brane), the membrana reticularis forms in simple folds a connected series of thimble-like 

 diverticula comj)osing the chamber layer. The complication of this folding increases 



