454 Mr. J. Thomson and Dr. H. A. Nicholson on the 



gentibus ; axe niiUo ; lateribus omnino cellulosis." From his 

 short description it appears that Dana included under this 

 name both simple and compound corals, having a central area 

 composed of septa and cells converging upwards (but without 

 a distinct columella), an external vesicular area, and a calice 

 with a conical prominence at the bottom, about which the 

 lamellge sometimes appear twisted. One of the three figures 

 given by Dana as illustrative of the genus is undoubtedly a 

 true Glisiophyllum as at present defined ; and it may with great 

 probability be surmised to be the form now known as C. coni- 

 septum, Keys., which, in this case, must be regarded as the 

 type of the genus. The other two figures represent a compound 

 coral, apparently a species of Lonsdaleia. 



Milne-Edwards and Haime defined the genus Clisiopliyllum 

 (Brit. Foss. Cor., Introd. p. Ixx, 1850) as follows: — "Corallum 

 simple, turbinate. Septa well developed, and rising towards 

 the centre of the calice so as to form a spurious columella, 

 but not twisted." Subsequently (Pol. Foss. des Terr. Pal. 

 p. 409) they enlarged their previous definition somewhat, 

 whilst preserving its essential features, and, in particular, 

 retaining the erroneous view that the subconvolute lamina of 

 the central area are the primary septa. The species which 

 they select as the type of the genus (viz. G. Danaanum) is 

 stated to possess a large and deep fossula — a very unusual 

 feature in the genus. 



At the same time Prof. M'Coy (Brit. Pal. Foss. p. 33, 1851) 

 defined the genus CUsiopliylhim as follows : — " Corallum simple, 

 branched, or aggregate, with vertical radiating lamellge ; a thin 

 epitheca or outer wall ; internal structure : — (vertical section) 

 central area composed of small vesicular plates and cells con- 

 verging or arching upwards towards the centre, so as to form 

 a conical boss in the cup ; no distinct central axis ; outer area 

 of small cellular structure, inclining in the opposite direction 

 or upwards and outwards ; separation between these areas 

 formed by an intermediate area of larger, nearly horizontal 

 cellular structure ; (horizontal section) a large central area 

 of small, irregular, cellular texture, from which the primary 

 lamellge radiate to the outer walls ; intermediate zone with few 

 vesicular plates between the lamellaa ; outer zone having the 

 primary and secondary lamellae connected by very numerous 

 vesicular plates." It will be seen from the above that most 

 of the essential features in the structure of Glisiophyllum are 

 rightly represented in the descriptions and figures given by 

 M'Coy. More especially has he the merit of clearly recogni- 

 zing the triareal structure of the corallum. The chief defects 

 of his definition lie in his supposition that the ascending 



