24 DIPLOHELIA. 



not been very extensive, still they are probably sufficient to illus- 

 trate and partly confirm Dr. Duncan's views. 



The following are the species examined, keeping the usual generic 

 names : — 



1. LophohcUa iwoUfera M.-Edw. & H., Florida and North European 



seas. 



2. Lopliohelia cxigua Pourt., Florida. 



3. AniphihcUa oculata M.-Edw. & H., North European seas. 



4. Amphihdia Carolina Pourt., Cuba. 



5. Amphihelia iufundibuUfera Lamk. sp.. East Indies ? 



6. Amphihelia miocenica? Seg. (^. ramea Sars), Norway. 



7. Diplohelia rarislella M.-Ed. & H., fossil, France. 



8. Diplohelia profunda Pourt., Florida. 



The first and second have no columella, entire se^^ta, thin 

 caenenchyma (but quite distinct) ; the third has also entire septa, 

 a small columella, thick caenenchyma ; the fourth, entire septa, no 

 columella, thick caenenchyma ; the fifth, serrate sej)ta, no columella, 

 thin ciBuenchyma; the sixth, serrate septa (?), a columella, thin 

 caenenchyma ; the seventh and eighth, serrate septa, small colu- 

 mella, moderate caenenchyma. 



It is evident from this arrangement, that, giving to the above 

 characters the weight usually attached to them, these seven species 

 would be assigned to at least five distinct genera. The distinction on 

 account of presence or absence of caenenchyma falls to the ground, 

 since it is only a question of more or less. The same might be said 

 of the presence or absence of columella, since it is almost absent in 

 some of the corallites of Amphihelia oculala for instance, and, on the 

 other hand, rudiments can be found in some corallites of Lophohelia 

 prolifera. There remains, then, only the serrate or entire edge of 

 the septa, which in some fixmilies of corals constitutes a character 

 for their division into subfamilies. It is in many cases a very 

 unsatisfactory character, particularly to the paleontologist, and has 

 given rise to serious mistakes, an example of which will be shown 

 in another part of this paper (AstrocjBnia). 



For the present, and considering the small number of species under 

 comparison, it seems proper enough to combine the genera Lophohelia 

 and Amphihelia into one, as there is really no permanent character to 

 separate them. The genus Diplohelia might, however, be kept for 

 those species in which the corallites never appear individualized, even 

 when young, but form, as it were, part of the branch with the same 

 diameter throughout. The character is not a very good one, perhaps, 

 still there is something distinctive in it which strikes at first sight. If 

 living specimens of Diplohelia profunda can be procured (mine are all 

 more or less worn), some otjier characters may be detected. 



