390 ESCIIARIDJE. 



leaving the general question as to the grouping of the 

 Reteporine forms to be settled after a more extended 

 study of their structure and morphology than is possible 

 within the limits of our Fauna. 



Smitt has dismembered the genus Retepora, and has 

 placed our R. Beaniana in his genus Eschara as the com- 

 panion of Porella compressa, Porella Itevis, and other 

 species. In this determination I am quite unable to 

 agree with him, as, besides other differences, R. Beaniana 

 seems to me to depart widely from the zooecial type of the 

 genus Porella. 



It may be remarked that amongst a considerable pro- 

 portion of the species which have been hitherto ranged 

 under the genus Retepora there is a large amount of 

 general agreement, apart from any consideration of the 

 minuter details, or the mere peculiarity in the branching ; 

 they have many salient features in common, and leave on 

 the mind of the student the impression of strong affinity 

 as existing amongst them. The mode of origin and the 

 general character of the zoarium seem to be much the 

 same in all of them ; the existence of avicularia on the 

 dorsal surface is a very usual character; these appen- 

 dages are exceptionally numerous, and their prevalent 

 forms are similar to a large extent ; the fissured ovicell is 

 commonly (though not universally) present. It is possible 

 that in these and other characteristics we may have the 

 indications of a natural group, under which the various 

 modifications in the structure of the orifice &c. which 

 actually occur may be properly ranged. But the mate- 

 rials for a judgment on this point arc at present wanting. 



