MADEEPOEA. 25 



Rev. d. Zooph. d. Antilles, p. 32 ; Pourtales, lUustr. Cat. Mus. Comp. Zool. pt. iv. p. 84 ; 



L. Agassiz, Mom. Mus. Comp. Zool. 1880, vol. vii. pi. xviii. ; Quelch, 'Challenger' Reef Corals, 



p. 149 ; Rathbun, Proc. U.S. Nat. Mus. 1887, vol. x. p. 13. 

 Heteropora regalis, Ehrenberg, Corallenth. d. roth. Mceres, p. 111. 

 Madrepora regalis, M.-Edwards & Haime, Coralliaires, t. iii. p. 139. 

 Heteropora laxa, Ehrenberg {non Lamarck), Corallenth. d. roth. Meeres, p. 110. 

 Madrepora mperba, Klunzinger, Korallth. d. roth. Meeres, Th. ii. pp. 19, 20, pi. iii. fig. 1, pi. iv. fig. 5, 



pi. ix. fig. 15 ; Miibius, Beitr. z. Moerosfauna Mauritius, p. 45 ; Faurot, Arch. Zool. exper. 1888, 



t. vi. p. 119. 

 Madrepora secunda, Ortmann, Zool. JB. 1888, Bd. iii. p. 150 (part.). 



A. Forma palmata. 

 Corallum frequently fiabellate or palmate ; fronds large, thin, and usually solid quite to 

 the margin, flat or curved, often several radiating from an incrustiug base. Some specimens 

 are short, stout, vasiform, with a thick pedicel and broad base, branches quite indistin- 

 guishable. The fiabellate forms consist of fronds often 60 cm. long and 40 cm. or more 

 broad, forming solid plates about 8 mm. thick at the apex and 1 to 2 cm. near the base. The 

 fronds may be entire or divided by narrow fissures into lobes. In other cases they are 

 alciform {M. alces, Dana), with the branches composing each lobe confluent quite to the 

 apex. In the majority of specimens the branches are only recognizable near the margin of 

 the corallum, but in some their course is indicated by furrows on the surface. Axial 

 corallites sometimes scarcely recognizable, particularly in vasiform specimens. In other 

 cases the marginal divisions of the branches bear axial corallites 2 to 2'5 or even 3 mm. 

 diameter and 1 to 3 mm. exsert. Wall sometimes rather thin, but usually thick and 

 porous, strongly striate exteriorly; the largest corallites usually occur in branches which 

 are comparatively free near the apex. Radial corallites prominent on both sides of the 

 frond or only on the upper one. Prominent radial corallites tubular, with a more or less 

 oblique aperture; sometimes half-tubular, lahellate, or nariform, often unequal in length, 

 1 to 4 mm. or even 5 mm., and 1 to 2 mm. thick, but usually between 1'5 mm. and TS mm. 

 They arise at an angle of about 45° on the branches, but in the fiabellate portion are more 

 spreading, frequently at right angles. A variable number of immersed corallites occur 

 between the others; in some specimens they are not numerous, in others quite half the 

 corallites are immersed. The length, as well as the prevailing form of the prominent 

 corallites, varies very much in different specimens, even from the same locality. Star 

 little developed, consisting usually of slightly prominent directive septa and four others 

 which are rudimentary. Corallum always porous and reticulate in section near the apex, 

 but frequently dense below ; surface spongy-echinulate ; wall striate and usually echinulate 

 near the base ; the striae are much more prominent in some specimens than in others. 



The majority of the specimens which have come under my notice do not suggest a very 

 close affinity to the arborescent forms proUfera and cervicornis, and for some time I was 

 inclined to regard them as distinct. Nevertheless a number of intermediate forms occur, 

 chiefiy in the collection of the British Museum, which appear to render it necessary to 



