124 Notices of Memoirs. 



was sufficient to cover the incipient coral. The shape of its nucleus, 

 as described above, is in accordance with such a supposition, the 

 nucleus being at first quite circular, as the calice of the coral 

 itself was. The specimen, which is still covered by its operculum, 

 is at its basis cylindrical, then acquires a semiconical shape, having 

 one side flat — the bottom side — and one convex. First, at a distance 

 of 9™™ from the basis, the whole length of the coral being IG'"™, it is 

 quite four-sided. The bottom valve is the only one that is com- 

 pletely homologoiis, as to its interior surface, to the single-valved 

 operculum of the genera Calceola and BMzopJiyllum, as I endeavoured 

 to point out in my former paper. Its median ridge is very faint, 

 and it is at the basal or cardinal line above that ridge provided with 

 a pit into which, just as in Calceola, no doubt the blunt edge of 

 the corresponding calicular septum has been inserted. The upper- 

 most valve, on the contrary (pi. xxx., fig. 8, in Ofversigt Veten- 

 skaps-Akademiens Forhandlingar), has a very large median ridge, 

 larger than in any of the other valves, and this large prominence 

 corresponds with the deep septal groove in the calice. The triangular 

 valves — those of the left and right side — are quite similar to each 

 other, and resemble also the uppermost valve, although the median 

 ridge is not so prominent. The valves are with their basal or hinge 

 line so closely affixed to the borders of the calice, that no opening is 

 seen, excepting in one of the crushed valves, which is a little lifted, 

 so as to show how the teeth-like prominences on the valve are 

 lodged in the interstices between the uppermost edges of the septa. 



In the Proceedings of the Eoyal Academy of Sciences in Stock- 

 holm (Ofversigt Vet. Ak. Forhandlingar), 1868, page 421, pi. vi., 

 fig. 4, 5, I described a new species, Cystiphyllum prismaticum, and 

 I also then, as well as in my first paper on the Corals (Gbol. Mag., 

 1866, page 411, PL XIV., Fig. 22, 23), gave a description of its 

 operculum. This coral is formed as an obtusely four-sided prism, 

 and has now been found in sufficient numbers to show not only 

 that the animal shed its operculum, and formed a new one at 

 intervals, some bearing two opercular valves above each other, 

 affixed to the same side below the calicular rim, but also that its 

 calice was closed by several valves on different sides, these being still 

 attached to at least two sides in some specimens. But it cannot now 

 be decided whether there were only four valves, as in Goniophyllum, 

 in accordance with the four-sidedness of the coral, or more. 



It is of great interest to find that these Palaeozoic operculated 

 corals have their counterparts among the recent corals. Prof. Koel- 

 liker in 1866, in his "Icones Histiologicas," 2te Abtheil. 1 Hft. 

 p. 135, described an operculum consisting of eight valves in some 

 species of the genera Primnoa and Paramuricea. Such species, ac- 

 cording to him, are Primnoa lepadifera, L., and Param. placomns, L. 

 Through the great kindness and liberality of Prof. S. Loven, I have 

 been enabled to examine specimens of both these species, as well as 

 of Primnoa verticillaris, L., and of an undescribed species of the genus 

 Calyptrophora, J. E. Gray (Proceed. Zool. Soc, 1866, p. 25), In 

 Param. placomus and Primnoa verticillaris these opercula are incom- 



