30 DE. G. C. BOUBNE OK 



variable in this case, it seems probable tbat T. armatus, Mich. 

 and T. perarmatus, Tallavignes, are only varieties of one 

 species. T. Mantelli has six spines. It is remarkable that 

 two quaternary costae cooperate with each primary costa in 

 the formation of a spine, and in one case as many as five 

 costae unite to form a spine, viz., one primary, one tertiary, 

 and three quaternary. In three specimens the fourth cycle 

 of septa is complete, in the other two specimens two quaternary 

 septa are missing in one of the systems adjacent to the long 

 axis of the calyx, and in each case the tertiary septum, which 

 they would, if present, have embraced, is devoid of a palus. 

 But the missing quaternaries ;are not adjacent to the primary 

 septum, which is devoid of a spine, as described by M.-Edwards 

 and Haime for T. armatus. 



The following are the measurements of the five specimens : — 



Note. — Since this paper was written Dr. A. Alcock has 

 published an account of three species of corals, very similar 

 to the form described above as Trocliocyaihus liastatus (Report 

 on the Deep-Sea Madreporaria of the ' Siboga^' Expedition, Leiden, 

 1902). Two of these he has described under the names of Odonto- 

 cyathus sexradiis and Odontocyathus Stella ; the third specimen 

 he has not named because it was in too imperfect a condition for 

 accurate diagnosis. 



"When my paper was read before the Linnean Society it was 

 naturally suggested that, as the Funafuti specimens are so very 

 similar to those described by Dr. Alcock, they might belong 

 to one of his species, and certainly to the genus Odontocyathus, 

 Moseley. 



The Funafuti specimens which I have named Trocliocyathus 

 Tiastatus differ from Odontocyathus sexradiis in the following 

 particulars : the primary septa are not so conspicuously exsert ; 

 the edges of the bowl-shaped corallum are not scalloped ; there 

 are only four cycles of septa, instead of five and parts of a sixth 

 as in O. sexradiis ; the pali in front of the tertiary septa are by 



