No. 2.] NICHOLSON — NEAV FOFSILS. 1411 



line to two lines, bearing upon their upper surface imperfect 

 septa which extend from one tabula to another when the tabulae 

 are remote by the former distance only, but which otherwise do 

 not do so. Septa alternately large and small, distant from one 

 another about a third of a line. Tabula3 of the central area 

 closely approximated, from three to four in the space of two 

 lines, flat or slightly flexuous, the septa only slightly encroaching 

 on them. Epitheca with numerous constrictions of growth and 

 encirchno' nnnulations, as well as obscure longitudinal striae, . 

 Dimensions unknown, but certainly attaining a diameter of three 

 inches. 



In most of its essential characters this species agrees with B. 

 decorticatinn, Billings, of which perhaps it may turn out to be 

 only a variety. It is, however, distinguished by the apparently 

 constant peculiarity that the tabulae of the outer area are very 

 closely set, much more closely than in B. decortlcatum. Thus, 

 typical specimens of the latter exhibit only from three to five of 

 the curved tabulae of the outer area in the space of an inch ; 

 whereas examples of i^. approximatain present ho less ilum from 

 ten to fourteen tabular in the same space. Whether this charac- 

 ter is one of specific value or not, may be questioned, but I think 

 it advisable to refer the specimens w^hich exhibit it, provisionally 

 at any rate, to a new species. 



Locality and formation . — Corniferous Limestone of Port Col- - 



borne. 



Genus Heliophyllum (Hall). 



The genus Heliopliijllum is very closely allied to Cyatliopliyl- 

 him, and the following are the definitions of it, given respectively 

 by Milne Edwards and Haime, and by Mr. Billings : 



1. '^ Corallum simple. Septal apparatus well developed, and 

 producing lateral lamellar prolongations, which extend from the 

 wall towards the centre of the visceral chamber, so as to repre- 

 sent ascendins; arches and to constitute irre2;ular central tahulce,. 

 and which are united towards the circumference by means of 

 vertical dissepiments." (Milne Edwards and Haime.) 



2. '• Corallum simple or aggregate ; radiating septa well de- 

 veloped, obliquely striated on their sides by thin elevated ridges, 

 which extend from the outer wall in an upward curved course 

 towards the centre. These ridges are connected by numerous 

 thin laminae, which divide the spaces between the septa into 

 small sub-lenticular cells. The transverse diaphragms are thin^ 



