32 DR. a. C. BOUENE ON 



Should we, then, place them in the genus Trochocyatlius, or create 

 a new genus for their reception ? After considering this point 

 carefully, I decided that there was no occasion for creating 

 a new genus, for there are no characters, either of septa, costse, 

 costal spines, basal scar, pali, or columella, which do not come 

 under the definition of the genus Trochocyatlius as given by 

 Milne-Edwards and Haime, a definition which has never been 

 altered by any subsequent authority. In these days, when 

 a series of imperceptible gradations is held to be a good reason 

 for uniting species formerly considered distinct, it is no time 

 to establish new genera among forms connected by equally 

 imperceptible gradations. 



2Sth January, 1903. G-. C. B. 



[Addendum. — It was only after this paper had been sent to 

 the press that I received three discoid corals which, on account 

 of their small size, had been overlooked, and were found again 

 when the collections from Funafuti were being finally sorted for 

 distribution to various museums. 



The specimens in question are minute discoid forms, the 

 largest measuring 4 mm., the smallest 3 mm. in diameter. In 

 the smallest specimen there are sis costae, corresponding to six 

 primary septa, which are more prominent than the rest ; in the 

 two larger specimens there are six distinct but short and stout 

 costal spines, corresponding to the six primary septa. Coming 

 as they do from the same locality, these small discoid corals may 

 safely be identified as the young forms of Trochocyatlius liastatus. 

 They are of considerable interest, for they show that the free 

 forms of this species are derived by strobilization from a nurse- 

 stock or trophozooid, and that the arrangements of septa, pali, 

 and spines characteristic of the adult are the result of secondary 

 growth after the young forms have separated from the nurse- 

 stock. 



The three specimens are shaped like flat discs, the smallest 

 being rather less than 1 mm., the largest about IJ mm. in 

 thickness. The upper and lower surfaces of each present a large 

 scar of attachment, extending over nearly the whole diameter of 

 the disc. On one surface, which may be called the lower 

 surface, the interseptal loculi are more or less filled up with 

 a compact calcareous deposit, so that the outlines of the septa 

 are obscured or hardly distinguishable. On the other surface 



