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PROCEEDINGS OF THE 



[April, 1857. 



r C AMPANULARIDiE , 



SERTULARIDiE. 



if Thaumantias. 

 Thaumautiadae 1 Staurophora, 

 ( Tiaropsis. 

 f Geryonopsis, 

 I Tima, 

 Eucopidae J Eucope, 



j Eucheilota, 

 | Epenthesis, 

 [ Campanularia. 



C Sertularia, 

 Halecium, 



J Thuiaria, 

 Plumularia, 

 Aglaophenia, 

 Antennularia. 



2nd Sub-Order. 

 Exostomata. 

 Digestive trunk 

 always free. Mar- 

 ginal capsules al- 

 ways present at 

 an early stage of 

 growth. Disk in 

 free forms, most 

 usually shallow. 



Eh <u 



{Circe, 

 Persa, 

 Aglaura ? 



Trachynemidee..l^ ach y nem a, 

 J [ Rhopalonema, 



Stomobrachidse. . 



f Stomobrachium, 



( Mesonema. 



Geryonidee ( Geryonia, 



J ( Ijinope. 



Rachostoma. 



{ Cunina, 

 | ^Egina, 



^EGINID^E \ ^Egineta, 



\ I iEginopsis, 



\ [Polyxenia. 



This scheme exhibits as nearly as I have hitherto been able to 

 make them out, the actually known, and in cases where there is no 

 actual knowledge, the probable embryological relations of the 

 Hydroidae. - It is probable that such relations will hereafter serve 

 as our principal guides in determining families. It is possible 

 also that the families will be even more numerous than those 

 already established among the Hydroid polyps or larvae, and that 

 such groups as the Oceanidse and Hippocrenidse will hereafter en- 

 joy the rank of families, as well as the marked group of iEginidaa, 

 which it is not unreasonable to expect will have to be sub-divided. 

 Certainly the generic limits employed hitherto have been often 

 too comprehensive. Prof. Agassiz's Hippocrene super ciliar is diners 

 from the Bougainvillea Brittanica and B. nigritella, by the posi- 

 tion of its ocelli, and this difference is generic. The Oceania 



