GENERA OF FA VOSITID&. 53 



M'Coy and Lonsdale were right in regarding F. basaltica, 

 Goldf., as a mere variety of F. Gothlandica. 



The tabula in F. Gothlandica are typically " complete " 

 that is to say, they pass completely from one side of the 

 visceral chamber to the other. I am able, however, from 

 specimens in my own possession, to entirely corroborate the 

 statement of Mr Billings (Canad. Journ., new sen, vol. iv. p. 

 1 02, fig. 2) that single examples, otherwise inseparable from 

 this species, exhibit in certain tubes the complete and compara- 

 tively remote tabulae characteristic of F. Gothlandica and its 

 allies ; while in others they show the incomplete, close-set, and 

 interlocking tabulae of F. hemispherica, Yand. and Shumard, in 

 virtue of which this latter was raised by Milne-Edwards and 

 Haime to the rank of a distinct genus (Emmonsia). In type- 

 specimens of F. Gothlandica from the Upper Silurian, there are 

 generally six to eight tabulae in the space of two lines ; but this 

 number may be exceeded, or may not be reached. Ordinarily 

 the tabulae are more or less flat and horizontal, but they are 

 very commonly conspicuously arched upwards, or more rarely 

 concave. The specimens with convex tabulae have usually 

 been separated as a distinct species, under the name of F. 

 favosa, Goldf. ; but a careful examination of a large number of 

 examples has led me to agree with Dr Rominger in thinking 

 that this character is very variable, and that it cannot be relied 

 upon as a specific distinction. Another peculiarity not uncom- 

 monly present is, that the tabulae are bent downwards at their 

 periphery into a series of infundibuliform depressions, giving to 

 the upper surfaces of the diaphragms a plicated or sinuated 

 appearance (PI. I., fig. 4). There are very often twelve of 

 these marginal depressions ; but there may be more or fewer, 

 and they are generally easily to be recognised in thin transverse 

 sections of the corallum (PL I., fig. 2). 



Lastly, the condition of the septa in F. Gothlandica is as 

 variable as that of the other elements of the corallum. In 

 most of the specimens the septa are quite obsolete, or can only 

 be recognised by the practised eye as minute inequalities of the 



