REPORT ON THE REEF-CORALS. 145 
length a primary septum corresponds exactly with its median axis, but on the other the 
septum has curved to one side at a distance of about 15 mm. from the median axis. 
Besides the large parent calicle, there are five other calicles which are more or less dis- 
tinctly developed. Of these the most perfect is situated close to the central one, and 
interrupts the course of the primary septum in the long axis. The other four are 
incompletely developed, and are situated between the smaller septa, where two of 
these are attached to a septum of a lower order; a widening of the interseptal space 
takes place at this point, and lateral thickenings, with incurving of the adjoining 
larger septa, indicate the formation of new septa for the developing calicle, which 
becomes complete when final division of the large septa takes place at the point of 
incurving. 
The long, fragile, nearly flat and thin corallum; the closely packed, even, rather 
thin and long septa; the large median calicle, with smaller calicles almost unperceived 
at a first glance, give a striking habit to this form and easily separate it from all others. 
Locality.—Tahiti. 
Section MADREPORARIA PERFORATA. 
Family EvpsAMMID&. 
Genus 1. Rhodopsammia, Semper. 
Rhodopsammia, Semper, Zeitschr. f. wiss. Zool., Leipzig, 1872, p. 257. 
= Duncan, Rev. Madrep., p. 182. 
A single species of this genus was obtained. The anatomy of this form has been 
investigated in detail by Mr G. Herbert Fowler.1 
Rhodopsammia parallela, Semper. 
Rhodopsammia parallela, Semper, Zeitschr. f, wiss. Zool., Leipzig, 1872, p. 258, pl. xix. 
figs. 1-4, 
Several specimens of this species in the collection show interesting differences from 
those described by Semper. In the largest calicles five complete cycles are present, 
while at the extremities of the long diameter orders of a sixth cycle are to be found. The 
primary and secondary septa are scarcely thicker than the smaller ones, much less so 
than is shown in Semper’s figure (fig. 4). The separate calicles are much less suddenly 
1 Quart. Journ. Micr. Sct., new ser., October 1885. 
(ZOOL. CHALL, EXP.—PART XLVI.—1886.) : Zz 19 
