PORIFERA. II. 185 



It was said in the preliminary remarks of the genus that a close relation, no doubt, existed between 

 the genera fophon and Pocillon. The two last described species, I. dubius and frigidus, also show some 

 features indicating such a relation. Thus both of them, and especially the latter, show a little larger 

 spines at the head-end of the acanthostyli, which is a feature common in Ectyonince. In /. dubius some 

 thinner acanthostyli are further found which have as a marked feature larger spines at the head-end, 

 but are connected with the thicker styli by all transitions, and considerably shorter acanthostyli are 

 found quite singly. In I. frigidus, as mentioned, the larger spines at the head-end of the styli are still 

 more marked than in dubius, and also here a few shorter acanthostyli are found, reminding of the 

 accessory styli of the Ectyonince. It is absolutely impossible to refer the two species to the Ectyonince, 

 as no spicules are found at all projecting from the fibres, and perhaps, as has often been hinted at 

 before, it is not improbable that the division into Mycalince and Ectyonina is no natural one, and will 

 have to be abandoned. 



lotrochota Ridley. 



The form varying, incrusting, thick cushion-shaped or irregularly massive, erect, more or less 

 leaf-shaped, or frequently more or less cylindric, unbranched or with few branches. The skeleton also 

 developed very variously, in the incrusting forms quite irregular and diffuse, consisting of spicules and 

 spicula-bundlcs ; in the massive ones it becomes an irregular, polyspicjilar network, and in the erect ones 

 it passes into a more regular arrangement, which may become quite regular with primary and secondary 

 fibre's. Spongin generally or always present to a higher or , most frequently , smaller degree. 

 Spic?ila: Megasclera : the skeletal spicules styli, sometimes witti a tendency towards a rounding of the 

 point, or a mixture of styli and oxea, or exclusively oxca, offenesf smooth, sometimes (I.spinosa) spined, 

 the dermal spicules tylota or strongyla, in a few cases with so different ends as to become tornostrongyla 

 or styli ; microsclcra pluridentate isancorcc unguiferer and birotulee, or only birotulce of one or two forms. 



1. I. varidens n. sp. 

 PI. XVIII, Fig. 1 a— e. 



Incrusting. The surface smooth. The dermal membrane rather thin, supported by erect or more 

 or less recumbent bundles of dermal spicules. The skeleton a diffuse -network of spicula-bundles and 

 single spicules. Spicnla: Megasclera : the skeletal spicules styli <rj/ — 0-608""", the dermal spicules tylota 

 0-298 — o-j8"""; microsclcra of two forms, isaucora- unguiferer with five to eight free teeth 0-054 — oo6^j""' r . 

 birotula: with nine to fourteen teeth 0-015 — o-o/8""". 



Of this species we have one entire specimen and a small fragment. The species seems to be 

 incrusting, the entire specimen forming an irregular incrustation growing on pebbles and other bottom 

 material. The specimen has a greatest extent of 25 mm , and the thickness is about io mm . The colour 

 (in spirit) is grayish yellow. The consistency is rather firm. The surface is about smooth. The dermal 

 membrane is a rather thin film, supported by bundles of dermal spicules most frequently highly 

 recumbent. Pores and oscula were not seen on the specimen. 



The In^olf-Expedttion. VI. 2, 2\ 



