OBSERVATIONS ON THE EUPLECTELLlDiE GENEEALLY. li 



suppleiiientarily be explained that tlie omission was made under 

 the impression that a distinct subfamily should be instituted to 

 receive the genera mentioned, together with certain others. I 

 have since come to see that this is not practicable ; in fact, all 

 the firmly seated Euplectellids known at present now seem to me 

 to form a group, which admits of no subdivision so as to repi'esent 

 more than one phylum. This is especially on account of the 

 intricate manner in which certain highly characterized hexasters 

 are distributed among, and combined in, the different genera. 

 So that, after all, they can not but be left to stand as one sul)- 

 family, the Corbitellimc, in contrast with the only other subfamily, 

 the Euplectellinte, of the family under consideration. The Cor- 

 bitellinse may then be characterized simply as : Euplectellidie 

 firmly attached to the substratum l)y compact base. 



It goes without saving that the definition of the Corbitellimc 

 as it stands in my Contriljution 11. and the list of the species 

 appended thereto are rejectable, the former as going too much 

 into particulars and the latter as Ijeing incomplete. 



Inseparably linked together as the Corbitelline genera ap- 

 parently are, the series may nevertheless be said to show a general 

 tendency of development in two directions. At the one end of 

 the series may be placed those forms, which, like Itcgadrella , 

 Gorbitella and the like, are of a tubular shape having the sieve- 

 plate and possessing Ijoth the floricome and the graphiocome 

 among the hexasters, EuplecteUa, and with it the Euplectellinre, 

 represents in all probability an off-shoot by special adaptation 

 somewhere from this end of the Corbitelline series. At the other 

 end may l)e placed those forms, e. g., Victyaulus, Hertwigia and 

 Saceocalyx, which, under variable external shap.es, have given rise 

 to such special hexaster-modifications as the discospiraster, the 



