CORALS FROM THE GAULT. 65 



found near Cambridge, in England ; at Gatis de Gerodot, Dienville, near Brienne (department 

 of the Aude), and Etrepy (department of the Marne), in Erance. Other specimens, which 

 in all probability belong also to this species, are designated in M. Michelin's collection as 

 having been found at Novion-en-Porcien ; at Macheromenil, in the Ardennes, and at the 

 Perte du Rhone, in the department of the Ain ; but we suspect that some mistake may have 

 been made in the labelling of the specimen which is designated in the same collection as 

 belonging to the chalk of Tournay, in Belgium. We must also add, that the fossil designated 

 by Professor J. Phillips under the name of Turbinolia conulus was found by that eminent 

 geologist at Speeton, in Yorkshire ; but its characters are not sufficiently well known for us 

 to be able to identify it with the above-described species, specimens of which exist in the 

 collections of the Geological Society, of the Museum at Paris, and of MM. d'Orbigny, 

 Michelin, and Milne Edwards. 



M. Al. d'Orbigny has lately given the name of Jjolocyat/ius 1 to those species of our 

 genus Trochocyathus in which the calice is circular. If this new generic division was 

 adopted, the species here described would be referred to it ; but that is not, in our opinion, 

 advisable. The calice, which is quite circular in a great many species of our genus 

 Trochocyathus, becomes slightly elongated in some, quite elliptical in others, and not only 

 would the line of separation be difficult to establish between these different forms, but 

 certain species which are evidently most closely allied by all then other organic 

 characters, would be. separated generically in the classification proposed by M. d'Orbigny. 

 We cannot, therefore, adopt his views in this respect ; but, in justice to that distinguished 

 palaeontologist, we must remark that the species 2 chosen by him as the type of his 

 genus Aplocyathus differs much in its general aspect from most species of our genus 

 Trochocyathus, and, when more completely known, may be found to present characters of 

 sufficient value to authorise the establishment of a separate generic group, which must 

 then be so defined as not to comprehend T. conulus, nor most of the other species that 

 have a circular calice. 



2. Trochocyathus Harveyantjs. Tab. XI, fig. 4, 4 a, 4 b. 



Trochocyathus Haryeyanus, Milne Edwards and J. Hahne, Monogr. des Turbinolides, in 



Ann. des Sc. Nat., 3 m ' serie, vol. ix, p. 314, 1848. 



Corallum simple, straight, short, almost hemispherical, and terminated by a very short 

 peduncle, the basal surface of which is concave. Costa distinct from the basis, and 

 delicately striated transversely ; the primary and secondary ones very prominent and sharp ; 

 those of the third cyclum well developed along the upper half of the wall, but those of 

 the fourth cyclum very small and obscure. Calice circular and fiat ; fossula shallow. 

 Columella well developed and papillose. Septa forming four complete cycla ; exsert, thin, 



1 Note sur des Polvpiers Fossiles, p. 5, 1849. 2 The Trochocyathus arrnatus. 



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