92 pRor. p. MAETiN Duncan's eevisiok op the 



group tlie corallites are united below hj their walls, and near the 

 calices by costae and esotheca. 



Distribittion. — Fossil. Jurassic : England. Eocene, Miocene : 

 Europe. — Becent. Indian Ocean, New Holland, north of Carib- 

 bean Sea. 



In thus limiting SympTiyllia, the genus is differentiated from 

 Mussa. 



M. de Pourtales has shown that the genus IsopJiyllia, Milne- 

 Edwards & Jules Haime, Pol. foss. des Terr, paleoz. &c. p. 87 

 (1851), is not separable from SympJiylJia. It; really only differs 

 in that the dentations of the septa are subequal instead of being 

 larger near the calicular margin. The species of Isopliyllia must 

 therefore be considered to belong to the genus SympJiyllia. 



After due consideration, it appears that the coral named Sym- 

 pJiyllia Etliericlgii, nobis, Suppl. Brit. Eoss. Corals, pt. 3, p. 19, 

 pi. vi. figs. 5-8, Oolitic Corals (Pal. See. Lond.), is correctly placed 

 Avithin the genus SympTiyllia and not in the following. 



G-enus Phtllogtea, Tomes, Quart. Journ. Geol. Soc. 1882, 

 vol. xxxviii. p. 430. 



" The corallum has a more or less depressed and massive form, 

 and is composed of a series of leaf-like expansions, proceeding 

 laterally from a parent corallite, the curled-up margius of which 

 unite and form sinuous cristiform ridges, the line of union of 

 which is very distinct in the younger examples, but much less so 

 in the older ones. Gremmations take place successively amongst 

 the elongated septa (which must be regarded as costae rather than 

 septa), and generally towards the extremity of the leaf, and a more 

 or less distinct line of calices is produced. There appears to be 

 no intercahcular gemmation. . , . When lateral gemmation has 

 ceased, the corallum only increases in height by the growth of the 

 single or serial coralhtes upwards- There is a common basal 

 wall, which is either naked or costulate, or has bands of rudi- 

 mentary epitheca. It is by the folding inwards of this outer wall, 

 and not by the growth of inner walls, as in Isastrcsa and Latimce- 

 andra, that the sinuous ridges are formed." 



Distribution. — Fossil. Oolite : England. 



This genus, according to its author, contains some remarkable 

 anomalies. A study of the figures given (pp. cit. pi. xviii. figs. 5-7) 

 of a species shows its eminently Symphyllian aspect, and the visible 

 calices are the result of fissiparity. I introduce the genus here with 

 doubt as to its value. Portions of a colony only have been found. 



