258 



PROCEEDINGS OF THE 



4th. The horizontal section of the 

 corallum is hexagonal in outline ; the 

 wall is stout and thick, and only very 

 sUghtly concave between the costse. 



5th. The surface of the corallum is 

 smooth and plain. 



6th. There are six septa, which are 

 united by a linear septal columella. 



7th. The endotheca is tolerably 

 abundant. 



8th. The diameter of the corallum 

 is ]-10th inch or less. 



&th. In the carboniferous hmestone 

 of Craigenglen, Stirhng, and Brockley, 

 Lesmahagow, Lanarkshire. 



4th. The horizontal section of the 

 corallum is nearly circular; there are 

 projections which correspond with the 

 costae ; and the wall is moderately thi ok . 



5th. The surface of the coraUum is 

 smooth. 



6th. There are six septa, which are 

 united by a linear septal columella. 



7th. The endotheca is scanty, and 

 the dissepiments are wide apart. 



8th. The diameter of the coraUum 

 is rather more than l-20th inch. 



9th. From the carboniferous hme- 

 stone of Craigenglen and Brockley. 



From tlie above descriptions it will be seen that the two species, 

 as described by Dr Duncan, have many characters in common, 

 and I am satisfied that, had he examined a lar2;er number of 

 specimens, he would have found every variety connecting them. 



In the first place, this coral has never, so far as I am aware, 

 been found with its extremities perfect, fragments occur from three 

 to four inches in length, but generally it is found in shorter pieces ; 

 these are of every diameter between y'g- and ^^5- inch or less. One 

 specimen 3 J inches in length, tapers in that distance from jV to ^^ 

 inch in diameter, showing that measurements from fragments of 

 various sizes are of no specific value. 



All the larger specimens are more or less flexuous, some of them 

 being much curved, and occasionally bent at right angles; this is 

 the case with both stout and slender specimens of the corallum. 



The curved hook-shaped processes which are described as one of 

 the principal specific characters of H. mirahiUs, I consider as of no 

 value in distinguishing that species, for we possess specimens of 

 every diameter as formerly quoted, showing tliese little booklets. 

 On nearly every specimen which is found embedded in the shale, 

 they may be exposed with careful manipulation. Indeed, it seems 

 to have been the perfect condition of the corallum, large or small. 

 In weathered specimens of the steins, found lying upon the shale- 

 banks, the booklets are always broken off, but their bases may still 

 be traced upon the costse, or in the grooves to which they were fixed. 



Dr Duncan states that H. Lijelli is only occasionally tuberculated, 

 but the specimen of this species which he figures in pi. xxxL, fig. 



