1898.] COEA.LS TBOM THE SOUTH PACIFIC. 533 



lies deep down in the axial fossa, closing it below and not pro- 

 jecting appreciably above its first junctions \A-ith the septa. 



Depth of the calices to the top of the columella varying up to 

 4 mm. ; breadth about the same. 



Eotuma ; outer reef. 



This species is to be distinguished from P. intermedia by the far 

 more completely circumscribed calices. The wall, too, is thinner 

 and no ridges between valleys are found. The fossae have a far 

 less open appearance, the septa in P. intermedia sloping inwards 

 from the wall, more precipitously at first. 



G-enus Psammocoea. 



Psammocora, Dana, Zooph. p. 344 (1846). 



Coscinarcea, Edwards and Haime, Compt. Eend. t. xxvii. p. 496 

 (1848). 



Mceandroseris, Eousseau, Voy. au Pole Sud de D'Urville, Zool. 

 t. V. p. 121 (1854). 



Plesioseris, Duncan, Journ. Linn. Soc, Zool. xvii. p. 309 (1884). 



The genus Psammocora was placed by Dana among the Fuugida, 

 and diagnosed as follows :— " Attached Pungidaj, glomerate or 

 ramose ; tentacles of polyps obsolete, polyps not seriate ; interstices 

 sometimes flat, usually throughoub turgidly elevate, the surface, 

 then, consisting of excavate cells. Coralla porous ; orizimes 

 minute ; lamellse very minute, often indistinct, and very minutely 

 arenoso-denticulate, often irregular, not alternately smaller." 



The genus is represented by four named species in my collection, 

 of which I have examined P. ohtusangida and P. haimiana as types 

 respectively of the ramose and massive forms. In the former the 

 calices are superficial, the surface has generally a rather sandy 

 appearance, and the septa are thick and few in number (very 

 commonly 8). In P. haimiana the calices are very deeply ex- 

 cavate, with an appearance of distinct \\alls at the surface, and 

 the septa are thin and numerous (seldom less than 16). 



Fractures, made longitudinally and transversely, show that the 

 septa in P. ohtusangida are at first continuous between neighbom-ing 

 axial fossse. They are usually studded at the free surface with a 

 few rather wide, blunt spines, which are commonly rather broader 

 than the parts of the septa between. The septa under these 

 spines are thick and very solid, while the parts between are thin 

 and sparsely perforated ; the septa thus, in section, have a ridged 

 appearance. The ridges on neighbouring septa lie opposite to 

 one another, and in places are thickened and meet, forming 

 synapticula, which are accordingly arranged in vertical series. 

 In the middle of the septa, extending from fossa to fossa, the 

 synapticula are especially large and closely arranged, forming a 

 much perforated wall, which becomes thicker and more solid 

 below, partially, apparently, owing to trabeculse arising from the 

 sides of the septa. Commonly, on either side of this central row, 

 another Hne of synapticula is weU marked. In the centre of the 

 axial fossa is a small blunt spine, which does not appear to be a 



