194 CEYLON PEARL OYSTER REPORT. 



M. Edwards and Haime as H. roussetmi and afterwards as Stephanoseris rousseaui 

 are identical with H. cequicostatus. 



The genus Stephanoseris was created, M. Edwards and Haime tell us, to 

 contain the species first described by them as H. rousseaui, but subsequently found 

 to possess synapticula, the presence of which involved its removal to the Fungiidae. 

 Subsequent authors, including Duncan, have accepted the genus Stephanoseris, 

 the last-named remarking that he places it with much doubt among the Fungiidse, for 

 he could not find synapticula in any of his specimens. Omitting for the moment 

 any reference to synapticula, we find that S. rousseaui differs from H. cequicostatus 

 (1) in having costee of unequal size, the tertiaries being particularly large; ('2) in 

 having four instead of five cycles of septa ; (3) in the fact that the septa do not project 

 externally. 



Among the specimens in Professor Herdman's collection there are individuals 

 with all the characters of H. cequicostatus, and every intermediate grade between 

 these and individuals identical with S. rousseaui. Further, I have found well-marked 

 synapticular structures in every individual that I have examined, so there can be 

 no doubt that the forms described as Stephanoseris rousseaui are only varieties of 

 the forms described as Heterocyathus cequicostatus, and for reasons that I will explain 

 in the latter half of this paper 1 prefer to retain the latter name and to place the 

 genus among the Turbinolidse. Synapticula have, been found to be common to so 

 many different kinds of corals that their presence is no longer a reason for including 

 any given form among the Fungiidse. It should be mentioned that the synapticula 

 of Heterocyathus cannot be seen on mere inspection of the corallum, as they are 

 hidden by the swollen upper ends of the septa. In order to see them it is necessary 

 to make sections or to grind down the corallum below the level of the exsert septa, 

 when they are at once apparent, as is seen in fig. II. Thus one can easily under- 

 stand how both M. Edwards and Haime and Duncan, as well as other authors, 

 have failed to recognise their presence. The genus Psammoseris is described by 

 M. Edwards and Haime as resembling Stephanoseris (Heterocyathus) in almost 

 every respect, except that it has no pali. Not having access to the type specimens 

 of Psammoseris, I cannot speak with certainty on this subject, but I am inclined to 

 think that the genus was founded upon a variety of Heterocyathus, in which the 

 pali are so slightly developed as to be indistinguishable from the papilliform columella. 

 An inspection of Gardiner's excellent photographs of Heterocyathus (23, plate iii., 

 figs. 13 to 19) shows that such a reduction of the pali is not uncommon. Psamruo- 

 seris, like Heterocyathus and Heteropsaminia, fixes itself in the young state on a 

 gastropod shell, which it subsequently envelops, and in the adult the shell, and the 

 spiral basal cavity continuous with it, is tenanted by a Sipunculid of the genus 

 Aspidosiphon. I shall refer to this interesting association in a subsequent part of 

 this paper, and I give in the second part a detailed account of the anatomy and 

 minute structure of the corallum of Heterocyathus. 



