﻿SPONGES. HALLiLANN. 



155 



labelled ''Ecliinotwnia iiicriistans Carter type," and ''J'lunio- 

 halichondria jnauiDiillatu, Carter" respectively. These do not 

 satisfactorily corroborate Dend}'s assertion ot tht- synonymy 

 of the two names, since the latter slide show s a skeletal struc- 

 ture rather resembling that of the var. Ic-ris, and chelae \'ary- 

 ing from 13 to 26 /j in length; whilst in the former the 

 structure is much looser — somewhat similar to that of the \ ar. 

 iligifcita — and tlie chela? are only 12 to J2 ^i long. Without 

 wishing to attach any great importance to this discrepancy , I 

 simpl} point to the possibility of a varietal difference between 

 the sponges of Carter's two species. 'Ihe point can only be 

 settled by a re-examination of the original specimens. In 

 view of the existence of so many distinct but closely allied 

 varietal forms of this species, 1 it is necessary to proceed 

 cautiously in introducing synonymy ; unless a complete con- 

 necting series between two forms is known to exist, it is far 

 better — because less liable to lead to confusion — to treat them 

 as distinct varieties, each with a distinguishing name. Ac- 

 cordingly I would recommend that the Plumohalichondria 

 maniniilhifa of the "Challenger" Report be still considered a 

 variety distinct from the Echinonema i)icrustans. Carter. In 

 their description of this variety, Ridley and Dendy state that 

 the dermal skeleton is a reticulation made up exclusively ot 

 acanthostyles ; they also refer to their examination of a small 

 piece of the type-specimen of Carter's Pliiniolialichondria 

 mainmillata and mention concerning it that the dermal acan- 

 thostyles are intermingled with smooth oxea and not reticu- 

 lately arranged. These differences in the dermal skeletons of 

 the two sponges, they allowed, might very well prove 

 distinctive ; but the other characters showed so close a corres- 

 pondence that, under the circumstances, taking into account 

 the small size of the piece examined, and the possibility of some 

 amount of variation with age they did not consider it advisable 

 to distinguish the two by the introduction of a new name. Of 

 the varieties whose descriptions follow there is only one, viz., 

 digitata, in which the oxea have been found to enter into the 

 formation of the dermal skeleton ; accordingly, there is good 

 reason to believe that the presence or the absence of dermally 

 situated oxea may be a characteristic which is constant for 

 any given variety. The variety from 0\ ster Bay to which I 



1 In addition to the varieties described in this Report. I have before 

 me three others which are un(|uestionably quite distinct. Owing to the 

 scantiness of the material and its unsuitable state of preservation. I do 

 not venture to describe them. One is probably identical with a British 

 Museum sponge bearing the manuscript name " Clathrissa memhranacea, 

 Lendenfeld." Another bears a label in Lendenfeld's writing with the 

 name, "Clathrisfia a7-biiscidn," a species to which it bears some external 

 resemblance. The third is a ramose sponge of irregular growth with the 

 oscula situated singly at the extremities of branches. 



