MADREPORA. Al 
plates; wall costulate, the coste divided into dentate plates below. Axial corallites 
prominent, ?2°5 mm. diameter; radial corallites short, tubular, mostly 1°5 to 17 mm. long 
and ] mm. diameter, with a thin wall and circular aperture; a few smaller ones are scattered 
amongst the others, but none are immersed; most are placed at an angle of about 45°, and 
are therefore not so spreading as in M. formosa, Dana. One of the fragments from 
Amboina, referred by Quelch to M. gracilis, appears to me to belong here. Some of the 
specimens from Tahiti and Tongatabu are bushy, with proliferous twigs near the apex. 
Pacific Ocean: New Hanover, Fiji, Tahiti, Amboina, Tongatabu. 
a, Tahiti. H.M.S. ‘Challenger.’ 86. 12. 9. 236. 
6. Tahiti. H.M.S. ‘Challenger.’ 86. 12. 9. 237. 
oe 1]. 25. 235. 
c-e. Papeete Reefs, Tahiti. H.M.S. ‘ Challenger.’~ 86. 12. 9. 406. 
91. 9. 9. 2. 
f. Amboina. H.M.S. ‘Challenger.’ © 86. 12.9. 229. (= M. gracilis, 
Quelch, part.) 
gsh. Tahiti. ? 93.4.7. 74 & 76. 
a,j. Tahiti? if SRE Ye, 1/0) 6 Olle 
k. Tongatabu. J.J. Lister, Esq. [P.]. 91.3.6. 4. 
D. Prominent corallites short, erect, tubular, unless near the apex of a branch. 
a. Branches 2 cm. thick or more. 
18. Madrepora tylostoma. 
Heteropora tylostoma, Ehrenberg, Corallenth. d. roth. Meeres, p. 111. 
Madrepora tylostoma, Dana, Zoophytes, p. 489. 
The type specimens are much worn, and belong to a stout and laxly-arborescent species 
resembling M. secunda or M. muricata vay. cervicornis in habit. Stoutest branches 2°5 em. 
thick ; in one or two specimens they are fused together with large spaces between, measuring 
10 by Sem. The axial corallites are not preserved. The radial corallites are rather distant, 
spreading at right angles; very short tubular with an oblique aperture; some are sub- 
immersed and smaller ; they vary from 0 to 2 mm. in length, but most do not exceed 1 mm., 
diameter 1 to 15 mm. One cycle of septa is moderately developed, and a second is present 
in rudiment. Corallum dense, not reticulate im section; surface rather dense, reticulate, 
with blunt echinulations ; wall striate. 
Another specimen in the Berlin Museum, from Mauritius (Médius), differs from the 
types only in the sometimes less-oblique aperture of the radial corallites. Branches 1°5 cm. 
diameter and under. Axial corallites 2 to 2°5 mm. diameter, 2 mm. exsert. Surface and 
wall strongly spinose. 
Indian Ocean: Mauritius (Berlin Museum). 
