ASTR^EOPOR^E EXPLANAT^. 87 



Species 2. Astrffiopora horizontalia. (PL XXV. ; PI. XXXIII. fig. 8.) 



Description— CoraHum, a tliin, nearly horizontal plate with evenly drooping edges, which 

 are free from the substratum. The margin is so thin as to be almost sharp ; it is followed by 

 a well-developed epitheca, but not so closely as in ^. expansa, hence perhaps the tendency of 

 the edges to droop ; the upper surface evenly curved. 



Calicles small (1-25 mm.), diminishing in size near the edge, round, star-like, numerous, 

 about the diameter of a calicle apart. For some distance from the thin margin of the coraUum 

 the calicles appear to penetrate down to the epitheca. The margins of the incUvidual calicles 

 rise but very slightly above the level of the ccenenchyma as thin rings of granular vertical 

 projections arranged radiaUy, which internally run down continuous with the septal ridges ; 

 these projections are joined by a single layer of perforated mural tissue. 



The first cycle of septa is well developed aud conspicuous, the second is rudimentary, but 

 appears at the edge, and takes part in the formation of the marginal wall. 



Ccenenchyma. The interstices are more or less evenly floored with the typical synap- 

 ticular constituent which is perforated with round pores. The costal system of upright pillars 

 (echinula>) can be seen in all stages of development, giving the whole corallum to the naked 

 eye a rough graniUar appearance. Under the glass, the echinulie are seen to be very irregular 

 in shape and size, with an indefinite whitish fraying of their tips. 



The greater part of the smgle specimen of this new Astrfsoporan has been apparently 

 killed by'' an encrusting sponge. Three portions of its horizontally expanding edge were, 

 however, living when it was coUected. From its point of attachment it has grown out chiefly 

 on one side as a horse-shoe-shaped expansion, largely free, but touching the substratum here 

 and there. The coraUum is a Ught yellowish brown. It has a colony of smaU orange- 

 coloured sponges growing upon it. 



a. Bird Island, Seychelles (7 fathoms, sand and coral). (Type.) 



Species 3. Astrseopora myriophthalma. (Pis. XXV. and XXVI. ; PI. XXXIII. fig. 9.) 



Astrca myriophthalma, Lamarck, Aiiim. sans Vert,, ii. (1816) p. 260. 



Astrwopora vujriopUhalma, Blaiinille, Die. Sciences Natiu-clles, Ix. (1830) p. 343. 



Astraopara myriophthalma, Milne-Eilwards and Haime, Les Polypiaires fossiles des terrains palseo- 



zo'iques, 18.51, p. 141 ; and Los Coralliaires, iii. (1860) pi. E 2, fig. 4. 

 Non Astravpora mi/ricphthalma, Klunzingcr, Korallenthiero des rothen Meeres, 1879, p. 52. 



Description.— CoTaRmn flat, expanding, more or less circular, encrusting, with drooping 

 or horizontal edges. More or less irregularly humped in the older central portions ; general 

 aspect coarse ; colour of unbleached specimens bright red-brown. 



Calicles circular (2 mm. diameter), typically project as thin-walled cylinders (5 mm. lugh 

 and less), consisting of the ring of exsert septa with their costal echinulations, joined together 

 by a porous mural layer. The echinulations increase in length towards the base of the calicle, 

 where they are joined by trabecule, so that unless the caUcles are closely crowded there 



