190 CEYLON PEARL OYSTER REPORT. 



1848, was amended in the ' Hist. Nat. des Coralliaires ' ; in the former the columella 

 was described as " tres developpe"e," the pali as " tres dlevds," but both these 

 characters are exceedingly variable, and in the ' Hist. Nat. des Coralliaires ' the 

 definition of the structures in question runs thus : "La columelle est formde des 

 tigelles qui paraissent naitre du bord interne et inferieur des cloisons, et qui sont 

 d'autant plus elevees qu'elles sont plus dxtdrieures ; sa surface est papilleuse et 

 concave. Les palis paraissent se detacher egalement de la partie infdrieure des 

 cloisons, et se distinguent a peine des tigelles columellaires." The species of the 

 genus are not easy to determine with certainty. Lacaze Duthiers (33) gives 

 excellent photographs of P. striatus, and Duncan (11) gives several species from 

 different parts of the world, but all these are obviously different from the specimens 

 in Professor Herdman's collection. It should be observed that the initial and 

 therefore solitary corallites of the arborescent Cyathohelia closely resemble Para- 

 cyathus, the septal pali and columella being almost identical, and I am inclined to 

 think that several of the described species of Paracyathus are nothing more than 

 young Cyathohelise. 



Paracyathus stokesi, M. Edw. and H. 



There are three specimens of Paracyathus in Professor Herdman's collection ; 

 they were taken at different times from different localities and differ from one 

 another in details, but their resemblance is sufficiently close to lead me to refer them 

 all to P. stokesi, M. Edw. and H. (35, plate x., figs. 7 and 7a). 



Specimen a is from Trincomalee. The corallum is 17 millims. in height ; the calice 

 elliptical, its longer axis measuring 13 millims., its shorter axis 8 millims. The calice 

 is depressed at either end of the long axis. The septa correspond very closely with 

 M. Edwards and Haime's description of P. stokesi, but the fifth cycle is incomplete, 

 and the outer ends of the primary and secondary septa are scarcely, if at all, 

 thickened. The costae differ from those of P. stokesi, in being so slightly developed 

 that they are scarcely distinguishable at a short distance below the level of the 

 calice. 



Specimen b is from Galle. Height of corallum 14 millims. ; longer axis of the 

 calice 12 millims. ; shorter axis 9 millims. Septal arrangement as in specimen a, but 

 the septa are rather thicker externally. The calicular fossa is deeper, the columella 

 less develojjed, and the septal pali stouter and more prominent than in a. The costse 

 agree exactly with M. Edwards and Haime's description of P. stokesi; they are 

 rather broad, distinct to the base, and thickly covered with granules. 



Specimen c is from deep water near Galle. Height of corallum 1 4 millims. ; longer 

 axis of calice 7 millims. ; shorter axis 6 millims. This specimen resembles P. pro- 

 cumbens, M. Edw. and H, from the Eocene of Hauteville, in the following characters. 

 The corallum is curved and the calice inclined to one side ; the calice is subcircular 

 and rather deep ; the septa are somewhat exsert and their external ends project 



