269 



and with a well-chitinized compound operculiiin they must, I think, he referred 

 to tlie Mdlacoslecja, heing most nearly related to the genus Callopora. The species 

 luialina which Waters' with some doubt refers to the genus Megapora has be- 

 sides 6 larger, distal, marginal spines 1 — 3 very small, seated outside the frontal 

 area about half-way down, and as the second species M. ringens has an aperture 

 of (|uite the same form as that found in C. Poissoni, I think that these two spe- 

 cies are more nearly related to this interesting form than any other species hitherto 

 described. 



Having only examined dry colonies I have not been able to find a covering 

 membrane, but as the very low side-walls of the zooecia, when isolated, are sep- 

 arated from the arched frontal wall by an impressed line, I cannot doubt, that 

 lliis line indicates the distinction between a marginal gymnocyst and a frontal 

 cryptocyst, and as the spines arise just proximally to this line they are not, as I 

 originally thought, acropetal but marginal which can also be se6n by a com- 

 parison with the ancestrula. 



Family Euthyridae. 



The zooecia are provided with a slightly calcified cryptocyst, and in a larger 

 or smaller part of their surface the surrounding covering membrane is kept 

 distended by ridge-like or rod-shaped processes from the cryptocyst, which has 

 a number of superficial rosette-plates. The interzoa^cial \valls have scattered, 

 uniporous rosette-plates. A compound operculum. No spines and no heterozooecia. 

 There may be endozooecial o<i\'in with a projecting, membranous ecloofrcium. 

 Free, branched colonies. 



Summary of the genera. 



1) Ocrcia occur: the aperture provided with a narrow sinus; (the 

 covering-membrane is everywhere kept distended by narrow ridges 



from the cryptocyst) - Urceolipora Mac ("lillivr. 



(Calymmophura Husk ). 



1) No ooecia, but two dill'erent forms of zooecia; the aperture with- 

 out sinus, hut with an almost straight proximal margin: 



2) The IVontal cryptocyst forms a continuous calcareous surface; 

 llic covering-membrane is on the frontal as well as on the basal 

 surface distended by means ol' rod-shaped processes from Ihe crypto- 

 cyst Eiithyris Hincks". 



' U.'., p. :ii), lO'i. '-' 27, p. I(i4. 



