344 APPENDIX. 



Though the number of new or supposed new species is 

 so great_, the number of new genera is comparatively small, 

 not amounting to more than four. It has, however, been 

 found necessary considerably to modify the characters of 

 several other estabhshed genera, so as to include new 

 species. . 



With respect to the geographical distribution of the 

 species, my means of comparison have been pretty exten- 

 sive. They have been derived from the examination of 

 Mr. Darwin^s and Dr. Hooker's collections, placed at my 

 disposal by the kind liberality of Mr. Darwin, — a con- 

 siderable collection of South African species mainly pro- 

 cured from Mr. Bowerbank — and from the Collection of 

 British and exotic Zoophytes in the British Museum, for 

 the freest opportunities of examining Avhich I have to 

 thank Mr. Gray. From these various sources, and others 

 of less account, I have been able to examine species from 

 a very considerable extent of the earth's surface — more 

 especially in the Southern hemisphere, and to arrive 

 perhaps at as fair a \iew of the geographical distribution 

 of species as tlie present imperfect state of Zoophytology 

 will allow. 



POLYZOA. 



The number of species of Polyzoa is about fifty -four — 

 belonging to twenty-foiu' genera. Of these genera it is 

 beheved that four will be found to be new, or liitherto 

 undescribed, and it has been deemed requisite to modify 

 the characters of several others upon the more extended 

 survey of species afforded mainly by the present collection. 

 The new genera here instituted are : 



Calpidium JDidijmia 



Diachoris Dimetopia 



