APHKOPHYLLUM HALLENSE AND LITHOSTROTION. 57 



of the four species as the type, and therefore, according to 

 the strict interpretation of the laws of zoological nomen- 

 clature, Lithostrotion should be the name of the genus of 

 which E. Martin's floriforme is the genotype. But, since 

 there can be no doubt as to Fleming's intention (in taking 

 the pre-Linnsean name) of making Lhwyd's figure the geno- 

 type, and since the name Lithostrotion has been identified 

 for over sixty years with the genus that it universally 

 signifies, and any alteration now will cause very consider- 

 able confusion, I propose to retain the name Lithostrotion 

 as in the sense in which it is generally accepted. 1 



Description of Genus. 



External Characters. — The corallum is composite, but 

 may be either fasciculate or massive in habit, and the 

 corallites are accordingly cylindrical or prismatic; these 

 quickly attain their mature character and dimensions, but 

 grow to a considerable length. 



Internal Characters. — The septa are united to the 

 epitheca, and the major septa or most of them reach the 

 columella, the minor septa are prolonged only a small 

 distance beyond the theca. The fossulse are inconspicuous. 

 The counter septum is dilated along its inner edge to form 

 a styliform columella. The tabulae are well-formed conical 

 plates. The dissepiments are small of uniform size, and in 

 the large species build up a wide extrathecal area. 



With such a simple structure, it might be supposed that 

 the range of variation would be limited, nevertheless the 

 genus exhibits great variation. Exceptions maybe found 

 to all the above mentioned characters. In rare cases the 

 septa fail to reach the epitheca. Very frequently among 

 the fasciculate species, but only rarely among the massive 

 the columella is absent, and correlatively the septa are 



1 Q.J,G.S., (1916;, Vol. lxxi, p. 220-221. 



