98 R. F. Tomes — Palceozoic Madreporaria. 



Dimensiovs. — Diameter of the disk six-tenths of an inch ; length 

 of arm, two inches and six-tenths. This is less than in the living 

 state, as none of the arms are preserved up to their terminations. 



Affinities and Differences. — The fragmentary condition of the disk 

 prevents any definite conclusions as to the true generic position 

 of this form, but it agrees with Ophiurella closer than with any 

 other. It has the small disk with the upper and under surfaces 

 flattened, the lateral and ventral plates supporting spines, which 

 are specially jointed to the lateral plates. In all these essential 

 generic characters it agrees Avith OfMurella. I know of no figured 

 species from the Corallian rocks that resembles this Brittle-star. 

 The only form that occurs to my mind is Ophiurella bispinosa, d'Orb., 

 which has only been named, but was neither described nor figured 

 by the author. Our species is so widely different from all the 

 others, that there can be no confusion with them. 



This Brittle-star was obtained by Professor Buckman, F.G.S., 

 from the Calciferous Grit at Sandsfoot Castle, near Weymouth. 



IL— On Two Species of Paleozoic Madrepokaria hitherto 



NOT RECOGNIZED AS BRITISH. 

 By Egbert F. Tomes, Esa. 



THE present communication is the result of the examination of 

 a considerable number of small Silurian Corals, from Wenlock 

 and Colwall, made as long ago as 1883, and it was written with the 

 intention of its being communicated to the Geological Society. I 

 very much regret, however, that circumstances have arisen which 

 render it extremely difficult, perhaps impossible, for me to place 

 myself again in communication with that body. The paper appears 

 therefore in the pages of the Geological Magazine, a medium for 

 publication which I hope from time to time to have recourse to. 



Of the two species of Corals, an account of which I now lay before 

 the readers of the Geological Magazine, one represents an entirely 

 new genus, which I designate Semiphyllum, and the other is a species 

 of Cyathaxonia. 



Hemiphyllum, nov. gen. 



Cyathaxonia, M'Coy ? 



The corallum is simple, small, conical, and curved. It has a 

 porous structure, and is surrounded by a thin epitheca, which is more 

 or less rudimentary at the calicular extremity. There is a large and 

 spongy columella, but no septal fossette. The calice is circular 

 and bounded outwardly by a ring of spongy tissue, formed by 

 spongy septa united by porous endotheca, constituting a thick and 

 spurious wall. At the inner margin of this ring each pair of septa 

 coalesce to form a septum, which passes across the intervening space 

 and unites with the columella. All the septa are irregularly per- 

 forate, the punctures appearing to be due rather to their porous 

 nature than to any regularly arranged perforations. The loculi 

 appear to be open from the bottom to the top of the corallum. 



