24 DIPLOIIELIA. 



not been very extensive, still they are ])r()l)ably sufficient to illus- 

 trate and ])artlv confirni Dr. Duncan's views. 



The i'ollowing- are the species examined, keeping the usual generic 

 names : — 



1. L(ij)Jii>licll(( prolifcru M.-Ed\v. & H.. Florida and North European 



seas. 



2. L(ii>h(>lielia ccit/un Pourt,, Florida. 



3. Ainpltilii'Ila ocuhtia M-Ed\v. & IL, North European seas. 



4. Am/)hilicli(( canilinii P(jurt., Cuba. 



5. A))iji]tihi'll(i iiifi(ii(1iliiilij\'ra Landv. sp.. East Indies? 



6. A)iij)lillii'li(i iiihiccuica? Seg. (^4. ruini'ii Sars), Norway. 



7. Diplolii'lia rariiilclhi M.-Ed. & II., fossil. France. 



8. Dljilohcliu proftinda Pourt., Florida. 



The first and second have no columella, entire septa, thin 

 Ci>3neiichyma(but quite distinct); the third has also entire septa, 

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

 columella, thick civnenchyma ; the fifth, serrate septa, no columella, 

 thin c;enenchyma; the sixth, serrate septa (?). a columella, thin 

 cicnenchyma ; the seventh and eigiith, serrate septa, small colu- 

 mella, moderate cauienchyma. 



It is evident from this arrangement, that, giving to the al)ove 

 characters the weight usually attached lo them, tlie.se seven s])ecies 

 would ])v assigned to at least five distinct genera. The distinction on 

 account of presence or absence of canienchyma falls to the giound, 

 since it is only a question of more or less. The same might l)e said 

 of the ])resence or absence of columella, since it is almost absent in 

 some of the corallites of AiiijiJiIJicIhi ociiJatd for instance, and, on the 

 other hand, rudiments can be found in some <'oianites of LuiilinlicHn 

 jtriiUfi'i-d. There remains, then, only the serrate or entire i.^'A^^i.^ of 

 the septa, which in some familii's of corals constitutes a chai'acter 

 for their divisiou into sulifamilics. It is in many cases a \ery 

 unsatisfactory chanictcr, particularly to llie ])aleontologist, and has 

 given rise to serious mistakes, an example of which will l)e shown 

 in another i)art of this ])aper ( Astrocauiia ). 



For the ]u-csent, and considering the small luunber of species under 

 c()m])arison. it seeuis pro])er enough to cond)ine the genera l.ophohelia 

 and Auiphilielia into one. as there is really no permani'iit charai'ter to 

 separate them. The genus Diplolidia luiglit. liowt'\i'i', be kept for 

 those species in wliicli the corallites ncNcr a|)pear iudi\i(luali/.eil, e\H'n 

 when young, but form, as it were, ])art of the branch with the same 

 diameter throughout. The character is not a very good one, perha])s, 

 still there is something distinctive in it which strikes at first sight, if 

 living s])ecimens of Dij)h>helia jirofiDtda can be procured (mine are all 

 more or U'ss worn), some other characters ma\' be detected. 



