remarkahh Species of the Genus Lithostrotion. 321 



velopment by fission and latcro-calicular gemmation ; the 

 latter in the proportion of one to ten of the former. The 

 epitheca is thin, and there are delicate encircling lines and 

 shallow annulations of growth. The calice is moderately 

 deep and its centre is occupied by a styliform columella in 

 some corallites ; in others a portion of the septa coalesce and 

 extend inwards to the centre ; there they unite with septa 

 similarly arranged from the opposite side, and form a pseudo- 

 columella, which is alone developed between each of the 

 tabulge, whilst in several of the corallites the columella is 

 cylindrical. The septa are bilaminate and of two orders ; 

 the primary are variable in their inward extension, the 

 secondary extend inwards half the length of the primary, and 

 they are united by rectangular interseptal dissepiments. 

 The corallites are unequal in diameter and the septa are 

 variable in number. In a corallite 5 millim. in diameter 

 there are nineteen primary alternating with an equal 

 number of secondary septa. The tabulse are slightly inclined 

 upwards and occupy about half the total diameter of the 

 corallum. A fossula is present, but is hardly recognizable. 



Formation. Lower Carboniferous. 



Locality. Blackridge, Dumfriesshire. 



As regards the structural characters of the genus Litho- 

 strotion, these are so varied and the vicissitudes which it has 

 undergone are so numerous that it is desirable I should 

 briefly refer to a few of the characteristics upon which generic 

 identity is established. The name Lithostrotion was origi- 

 nally given by Luidius, ' Ichnographia ' (1760), to a group 

 of corallites figured on plate 23 of his work, and designated 

 ^^Lithostrotion sive Basaltes minimus striatus et stellatus." 

 There is, however, nothing to indicate its identity further 

 than the excellent delineation of the external aspect. 



In 1827 Dr. Fleming, in his ' History of British Animals,' 

 adopted the generic name for three species of Carboniferous 

 corals ; as I have elsewhere shown *, two of his species can- 

 not be identified as belonging to the genus. His Litho- 

 strotion Jloriforme has been correctly referred to McCoy's 

 genus Lonsdalia. 



Lithostrotion marginatum is not now in the collection ; a 

 reference to his description induces me to regard the two 

 fragments referred to as belonging to the genus Hetero- 

 phyllum, M'Coy. Lithostrotion striatum is still in the collec- 

 tion, and referred to by M. -Edwards and J. Ilaime as be- 

 longing to the same genus as Luidius's coral. 



* ' Transactions of Ediubur^'li Geological Society,' 1887. 



