18/6.] AND LITTORAL CORALS. 437 



Breadth of calices ^ inch. 



Locality. Caribbean Sea. 



This is allied to Oculina tenella, Pourtales. 



Sclerohelia hirtella, Pallas, sp. (Plate XLI. figs. 3, 4.) 



This fine species has been found at St. Helena, and as yet nowhere 

 else; and no other form comprehended by the genus has been de- 

 scribed. On a large Ostrea from the coast of St. Helena, there are 

 several specimens which would at a glance be referred to the genus 

 Sclerohelia ; and their examination, whilst it confirms this impres- 

 sion, proves the extraordinary amount of variation which the calices 

 may present. 



The specific diagnosis is as follows : — 



The corallum has a thick stem and many branches, the ccenen- 

 chyma being very thick, glistening, and finely granular. The costal 

 striae are slightly marked. The calices are alternate and oppo- 

 site on the young branches and are placed irregularly on the larger 

 ones, being generally but slightly prominent and shallow. The 

 columella is well developed, being made up of 7 or 8 papilla?. There 

 are three complete cycles of septa ; and some of the fourth are found 

 in one or two systems. The septa are very unequal and very pro- 

 jecting at the margin. The pali are well developed, and are placed 

 before the secondary septa. Diameter of the calices ^ inch. 



A comparison between this structural description and that which 

 can be given of the specimens on the Ostrea is very instructive. 



1. A large dendroid mass having three large branches, two of 

 which coalesce after some ramifications have been given off. 



Calice 1 . This is on the thick branch ; and its base is costulate, 

 and the surface granular. The shape is elliptical ; the septa are in 

 six systems ; and there are four perfect cycles in two systems, an in- 

 complete fourth cycle in one, and three complete cycles in the others. 

 The columella is composed of three oblong masses in a line ; the 

 pali are thin, rather long, and are placed before two secondaries and 

 two tertiaries on one half, and before two tertiaries and two secon- 

 daries in the other. 



In the next calice to no. 1 (2) the columellary masses have united 

 and have assumed a dense structure, arched above. No. 3 is a calice 

 on a small branch, the calice being rather more circular in outline ; 

 the columella has two side-papillae ; and two of the pali are wanting. 



And in another calice (4) the columella is as in no. 2 ; but the 

 pali are thick and broad. 



On other branches of the same corallum there are some calices 

 with four cycles of septa in four systems, and the fifth orders 

 wanting only in the half of the other systems ; and in some the 

 columella is long and solid, or long and incomplete, or round and 

 made up of many processes. 



On the surface of the trunk there are some calices which sur- 

 mount rather elongated buds, and the septal number is not over 24, 

 and the columella consists of one twist of a band-like structure 

 greatly resembling a styloid columella at the top. 



