160 MADREPORARIA. 



are much divided and bear numerous spreading twigs and short proliferations. In specimens 

 which extend obliquely the marginal branches closely resemble those of the cespitose form, 

 but the central ones are suberect, arcuate, distinctly tapering, and not so proliferous. Axial 

 corallites 3 to 4 mm. diameter (but not so stout on the smaller twigs), short cylindrical, 

 margin often a little roimded. Radial corallites much crowded, irregular, chiefly half-tubular 

 or short-labellate, with rounded or plane apex, sometimes distinctly compressed ; in some 

 specimens the form is more nearly nariform, or, if the inner part of the wall is at all 

 prominent, tubo-nariform, but in most specimens the inner part of the wall is not developed ; 

 diameter usually IS mm., more rarely 2 mm., with a few immersed cells scattered between. 

 The corallites usually remain more or less prominent quite to the base of the branches unless 

 on the under surface of oblique specimens. Star very prominent, but sometimes consists of 

 only 6 septa. Wall moderately thin and porous in the majority of cases, but the outer 

 part is distinctly thickened in the stouter corallites. Corallum porous ; surface spongy- 

 reticulate and echinulate ; wall striato-reticulate when thin, striate and echinulate if thicker. 



Var. pustulifera. (Plate XXVII. fig. B.) 

 Madrepora pusiulosa, Briiggemann {non M.-Edwards & Haime), Phil. Trans. 1879, vol. olxviii. p. 574. 



A variety which exhibits the same variations in habit as the type, and differs chiefly in 

 the form of the radial corallites, the majority of which are tubular with a somewhat oblique 

 aperture ; wall thin and striate as in the type. 



Indo-Pacific Ocean : Torres Straits and Great-Barrier Reef area, Rodriguez. 



a-c. Thursday Island. Saville-Kent Coll. 92. 6. 8. 248 to 250. 



d. Warrior Island. Saville-Kent Coll. 92. 6. 8. 252. 



e. Palm Island. Saville-Kent Coll. 92. 6. 8. 253. 



f-h. Low-Woody Island. Saville-Kent Coll. 92. 6. 8. 254 to 256. 



i. Rocky Island. Saville-Kent Coll. 92. 6. 8. 257. 



Var. pustulifera. 



a-f. Rodriguez. Royal Society [P.]. 7Q. 5. 5. 94 to 98 & 



100. {■= M. pustulosa,'&rvL^^.) 

 g. Thursday Island. Saville-Kent Coll. 92. 6. 8. 251. 



Division III. 



7. Subgenus CONOCYATHUS. 



Corallum corymbose, cespitose, bushy, subarborescent or reticulate, difiering chiefly from 

 Tylopora in having more slender apices to the branches and relatively small conical axial 

 corallites with rounded apex. The prominent radial corallites have a dense wall with the 

 margin rounded. The M. variabilis group shows an approach to M. brueggemanni var. 

 uncinata in the form of the radial corallites, but not in habit. The M. polymorpha group 

 leads to the form characteristic of M. rosaria and its allies. 



