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



for the sake of showing what has lieeu the fate of the Monaxonida at the hands of the 

 more recent authorities on the subject. We must now investigate the position assigned 

 to the group by Dr. Vosmaer himself. His system, based as it is upon all that was 

 good of the various old schemes, is naturally a great improvement upon any of its pre- 

 decessors. In brief outline it is as follows : — 



PORIFERA. 



Class I. POEIPEEA NON-CALCAEEA. 



Order L Hyalospongise ( = Hexactinellida). 



Order 2. Spiculispongife. 



Suborder I. Lithistina. 



,, II. Tetraotina. 



„ III. Oligosilicina. 



„ IV. Pseudotetraxoiiia. 



,, V. Claviilina. 



Order 3. Cornacuspongise. 



Suborder I. Halichondrina. 

 „ II. Ceratina. 



Class II. POEIFERA CALCARBA. 



Order 1. Homoccela. 

 Order 2. Heterocoela. 



Here the two suborders Clavulina and Halichondrina correspond to the Monaxonida, 

 and in the present work these two suborders are maintained as the two primary 

 divisions of the group, though it has been found necessary, after a careful study of the 

 large amount of material at our disposal, to modify somewhat the arrangement of the 

 smaller subdivisions. Dr. Vosmaer, we may here mention, subdivides the Clavulina 

 and Halichondrina as follows : — 



Suborder Clavulina. 



Families — 1, Polymastidse. 2. Suberitidae. (3. ClioniadEe.) 



Suborder HaUchondrina. 



Families — 1. Halicbondridse. 2.^Spoiigillid8e. 3. Desmacidonidae. 4. Ectyonidse. 



Quite recently ■* Professor Sollas has published the outlines of a slightly different 

 modification of already existing schemes, in which the meaning of the name Monaxonida 



' Sci. Proc. Roy. T)vh. Soc, vol. v. part ii. p. 112. 



