346 , APPENDIX. 



seem to be peculiar to the Australian seas. Ten of these 

 belong to the genus CateniceUa, and one to the closely- 

 allied Calpidimn^ three to Didymia and Dimetopia, and 

 one to DiachoriSj of which genus two other species are 

 found in the Straits of Magellan. 



The method according to which the Polyzoa are ar- 

 rangedj is, in the primary divisions at least, pretty nearly 

 identical with that indicated in the Synopsis of the Fami- 

 lies and Genera of Polyzoa Infondibulata, given in Dr. 

 Johnston's "British Zoophytes."* 



A few words, however, will be necessary to explain more 

 particularly the subsequent subdivisions here adopted. 



The order, Polyzoa infundibulata, is divided into three 

 suborders, coinciding very nearly with the Tubtiliporina, 

 CeUeporina, and Vesicularina of the work above referred 

 to, but as the characters of these suborders are derived 

 from the conformation of the opening of the cell, I have 

 thought it more convenient to name them accordingly. 

 The first suborder, having a round, simple opening to the 

 cell, is here termed the Ctclostomata ; the second, with 

 the opening of the cell filled up by a usually thin, mem- 

 branous or calcareous velum, and with a crescentic mouth 

 provided with a moveable lip, the Cheilostomata ; and the 

 third suborder, which might perhaps include the Hal- 

 cyoneUea of Ehrenberg, as well as the Vesiculariadse, dis- 

 tinguished by the existence of a more or less weU-marked 

 fringe of setse (sometimes only rudimentary) around the 

 opening of the cell when the animal is protruded, the 

 Ctenostomata. 



The following synoptical arrangement — which it must be 

 remarked, includes only the genera occurring in the 

 Rattlesnake collection — wiU serve to indicate the subse- 

 quent divisions. 



f Vol. 1, p. 263, 2nd Edit. 



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