MADEEPOEA. 89 



81. Madrepora tizardi. (Plate XI. figs. C, D.) 



Madrepora nasuia, Bassott-Smith (non Dana), Ann. Mag. N. H. 1890, vol. vi. p. 453. 

 Madrepora effusa, Bassett-Smith {non Dana), Ann. Mag. N. H. 1890, vol. vi. p. 454. 

 ? Madrepora pJantiginea, Bassett-Smith, Ann. Mag. N. H. 1890, vol. vi. p. 453. 

 ? Madrepora valida, Bassett-Smith, Ann. Mag. N. H. 1890, vol. vi. p. 453. 

 ? Madrepora eorymhosa, Bassett-Smith, Ann. Mag. N. H. 1890, vol. vi. p. 454. 

 Madrepora tizardi, Brook, Ann. Mag. N. H. 1892, vol. x. p. 464. 



Corallum corymbose^ a little concave above, 10 cm. high and 28 cm. wide. Under 

 surface oblique, reticulate or almost solid, with short stunted twigs in the general plane ; 

 lower surface almost naked if nearly solid, but otherwise provided with a few scattered verru- 

 ciform and immersed corallites, most of which are lateral. Branches 1*2 cm. diameter at the 

 base. Branchlets erect and relatively slender and elongate in some specimens, but stouter 

 and more stunted in others. Apices about 1-2 cm. apart. Length in the elongate form 

 4 cm., diameter 6 to 8 mm. at the base ; in the stunted form the length is about 3 cm. and 

 the diameter 1 cm. or slightly over. Axial corallites cylindrical, 2 mm. diameter or a little 

 over, 1 to 2 mm. essert; wall dense, margin sometimes slightly rounded, aperture very small. 

 Radial corallites ascending and rather distant, dimidiate, gutter-shaped or hooked-nariform, 

 with the outer margin curved, those below are dilated verruciform, with the aperture opening 

 inwards ; these gradually become less prominent, and all are immersed at the base of the 

 branchlets. The length is very variable, usually 2'7 to 4 mm., diameter about 1'6 mm., but 

 all the more prominent ones are distinctly compressed. At intervals elongate, compressed, 

 tubular corallites with oblique aperture occur, which indicate new outgrowths ; these are 5 to 

 8 mm. long, and 1"5 to 2 mm. diameter. At a later stage when such corallites form short 

 twigs with small corallites at the base, the axial corallite frequently has the terminal 6 or 

 7 mm. free from buds. The prominent corallites are frequently arranged in irregular longi- 

 tudinal rows, with immersed or subimmersed corallites between. The wall is a little 

 thickened and very dense, surface closely echinulate. The star consists of 6 or 12 septa, all 

 of which are usually narrow with the exception of the outer directive, which, in many cases, 

 especially in the hooked-nariform corallites, is very broad. 



Var. bsBocyathus. 

 Corallum broad, shallow, vasiform, the main branches becoming fused into a solid plate, 

 sometimes 36 cm. long, 24 cm. broad, and about 3 cm. thick, with small, scattered, sub- 

 immersed corallites on the under surface. Branchlets on the upper surface short and stout, 

 rarely 2 cm. long, and about 8 mm. thick. Axial corallites scarcely more prominent than the 

 radial ones which surround them, and of similar diameter, but with circular or only slightly 

 elliptical aperture. Radial corallites tubular, tubo-uariform, or dimidiate, with a more or less 

 tapered apex, and with many subimmersed or short labellate ones between ; diameter of the 

 more prominent corallites 1 to 1'6 mm., scarcely compressed, length rarely over 3 mm. 



China Sea : Tizard and Macclesfield Banks. 



