EEPORT ON THE MONAXONIDA. Ixiii 



The Halichondrina are divided by us into four families, the Homorrhaphidse.the Heteror- 

 rhaphidae, the Desmacidonidas, and the Axinellidse. To these von Lendenfeld adds a 

 fifth famUy, the SpongUUdaj/ but with the fresh-water sponges we have in this place 

 nothing to do, and we cannot afford the time and space to discuss their systematic position. 



The Homorrhaphidse are, obviously, a fairly satisfactory group. All have a reticulate 

 skeleton, all have diactinal megasclera, and all are without microsclera of any kind. The 

 group includes two subfamilies, the Renierinse and the Chalininse, each of which has long 

 been recognised, but hitherto these two subfamilies have been far too widely separated, 

 and that merely on the ground that in the Chalinin^e there is a greater development of 

 spongin than in the Renierinfe. Nearly all Eenierine sponges have more or less spongin 

 in the skeleton, and, as a matter of fact, it is impossible to say where the Renierinse end 

 and the Chalininse begin. The Chalinina3 appear to be derived from Renierinae (probably 

 polyphyletically, i.e., from several distinct genera), which, living in warm seas, have 

 developed a horny skeleton more or less at the expense of the spicular element. The 

 Chalininge proper, as we have already noted, are simulated by genera belonging to quite 

 distinct groups, which, living under similar conditions, have suffered a simdar change in 

 their skeletons. We have thus in the family Heterorrhaphidse the two genera Toxochalina 

 and Gelliodes, each with a distinct, well developed horny skeleton exactly similar to that 

 of true Chalininas, and also with diactinal megasclera, but each betraying its true position 

 by the presence of microsclera. By some authors (e.g., von Lendenfeld) the former genus 

 is included amongst the Chalininse, but we cannot agree to such an arrangement.^ The 

 mere possession of a horny skeleton is not sufficient guide to the systematic position of a 

 sponge, and this fact cannot be too strongly enforced. The Chalininse are very poorly 

 represented in the Challenger collection, and this is accounted for by the fact that they 

 are essentially shallow- water forms, and are rarely if ever met with in deep-sea dredgings. 

 Moreover, their range is rather a restricted one. On the other hand, in the large 

 collection of sponges obtained in Australian seas by Dr. R. von Lendenfeld, and now lodged 

 in the British Museum, the species of Chalininse are extremely plentiful and varied. Dr. 

 von Lendenfeld's descriptions of these sponges are now in course of publication, and we 

 hope that when they appear much will have been done towards putting the group on a 

 more satisfactory footing with regard to classification. 



about 0-44 by 0-011 mm. The chel.ie, on the other hand, are characteristically those of the genus Myxilla. Many, or 

 most of them, it is true, possess four teeth, but this condition is known to occur in at least one species of the latter genus 

 {Myxilla mariana, nobis ; cf. p. 138, footnote). There are a fair number of them in the preparation, and they are all, 

 or nearly all, equal ended and not, as stated by Schmidt, generally unequal ended. In short, Schmidt's figures and 

 description of these spicules are misleading in the extreme ; there can scarcely be a doubt that they are present as foreign 

 spicules, and such an occurrence is not at all uncommon. 



1 Proc. Zool. Soc. Land., December 21, 1886, p. 584. 



2 Mr. Carter carries this line of argument a step further, and actually includes a species of Homccodictya, characterised 

 by its remarkable chelate microsclera, in the genus Chalina, presumably because of the amount of spongin present in 

 the skeleton {Ann. and Mag. Nat. Hist., ser. 5, voL x. p. 111). 



