FAMILIES AND GENEEA OF THE MADREPORAEIA. 



39 



G-enus Amphihelia, Milne-Edwards Sf Jules Haime, 1849 (pars) ; 

 P. Martin Duncan, Trans. Zool. Soc. Lond. vol. viii. pt, 5, 

 p. 326 (1873), amended. 

 Syn. DiploJielia, Ed. & H. 



The colony is busli-shaped, and the gemmation is alternate, 

 marginal, and often double. The wall, with or without coenen- 

 chyma, increases in thickness at the lower part of tlie colony, 

 and often includes formerly free corallites. Corallites free, im- 

 mersed or coalescent. Columella exists. The septa are entire 

 or subentire, in six systems ; but there are few cycles. Costal 

 striae very variable in amount and direction. Ornamentation of 

 the wall granular or absent. Internal cavities do not fill ; 

 dissepiments absent, 



Distribution. — Fossil. Eocene, Miocene, Pliocene : Europe. 

 Cainozoic : Australia. — Hecent. Atlantic, Mediterranean, Carib- 

 bean, Australian seas ; Formosa. 



This genus absorbs Diplohelia, Milne-Edwards & Jules Haime, 

 1850. 



The genus Mnallhelia, d'Orbigny, 1848, was insufficiently dia- 

 gnosed as follows : — " Ce sent des Oculines, dont des calices 

 saillants sent lateraux et alternes de chaque cote des branches, 

 Calices pourvus de cotes en dehors," This description is not 

 distinctive. MM. Milne-Edwards and Jules Haime added to tbe 

 description, and slightly altered the name ; and M. de Eromentel 

 has made some very important additions to the characters of 

 some species, The presence of paliform lobes on some septa, 

 and the subentire condition of the septa were asserted by M. de 

 Eromentel, but they are doubtful points. The existence of hexa- 

 meral, octameral, and decameral types in the genus is extremely 

 interesting. 



Genus Enallohelia, Milne-Edwards Sf Jules Haime, Hist. 

 Nat. des Corall. vol. ii. p. 123 (1857), amended. 



Colony dendroid or bushy, or low compressed, and branches 

 uniting ; gemmation alternate and distichous. Calices small and 

 shallow, often oblique. Columella styliform, but often small and 

 even rudimentary. Septa few, slightly exsert, subentire, some 

 swollen at inner end, arranged in systems of six or eight or ten. 

 Cost^e visible near the calice ; wall-ccenenchyma considerably 

 developed. 



Distribution. — Fossil. Oolitic : Europe, England ? Creta- 

 ceous : Europe. 



