4 APPENDIX. 



of a tree. This is still more the case in Th. vermicular e, in which the central stem attains a high elevation, 

 bearing all the other windings of the loop ; in the last-named shell, the upright portion which covers the 

 visceral cavity is perforated by numerous pores, between which excrescences are sometimes seen, and that 

 these apertures were probably destined to allow a kind of current in the fluid filling the visceral cavity. 1 



From these researches, it seems probable that the Family Thecidiidae and Sub-Family Stringo- 

 cephaliDvE may be advantageously dispensed with, and their genera added to the great Family TERE- 

 BRATULIDiE. This view, which has been adopted by Mr. S. P. Woodward, has likewise been my opinion 

 for some time past, especially since the fortunate discoveries made by M. Suess. All that will be ne- 

 cessary is, therefore (in p. 51), to continue the connecting line from Terebratula down to Thecidium, and 

 to erase the family and sub-family above mentioned. 



Page 78. 



It is observed, that the most ancient Thecidium then known to us, was that found in the Triassic beds 

 of St. Cassian (Tyrol) ; but we subsequently read in the ' Bulletin de la Soc. Geol. de France ' (vol. x, p. 248, 

 1853), that Count Keyserling had discovered among the Carboniferous Fossils from Sterlitamak, a shell, 

 which he considers to belong to the genus Thecidium, and which he describes as follows : — " It is not new, 

 being the Anomia antiqua of M'Coy ; 2 but casts, partly deprived of shell, prove that it is a Thecidium, 

 ornamented by concentric waves, as in Th. tetragonum (Roemer), of which one valve is attached and per- 

 forated, while the other equally inflated exhibits a digitated arrangement which occupies nearly all the 

 interior. The oblique disposition of the processes of this arrangement (appareil) round the mesial crest, 

 similar to the leaves of a fern round their stem, has suggested to me the denomination Th. filicis for the 

 species. In analogous forms the digitations are directed forward, and more or less arched ; a crenulated 

 ridge following exteriorly all round the lateral digitated impressions, of which the second from the hinge 

 is the largest." We are at a loss to understand this remarkable fossil, as we cannot perceive in the figure 

 published by Professor M'Coy, any reason to believe that it belongs to Thecidium, and must therefore delay 

 the admission of the genus into the Carboniferous age, until M. de Keyserling has given us some more 

 tangible proof in the shape of illustration. 



Family — SpiRiFERiDiE. 



Page 84, note 3. 



Add — M. Suess objects to the term Atiiyris being applied to such shells as T. Herculea, 

 T. tumida, T. scalprum, &c., 3 that generic denomination having been originally employed by Professor 

 M'Coy, for T. concentrica, lamellosa, and other similarly organised species ; and that we cannot admit the 

 new version proposed by the learned professor in his subsequent work on the ' British Palaeozoic Fossils in 

 the Cambridge Museum.' If the denomination Athyris is to be removed on philological grounds, M. Suess 

 would adopt Spirigera, D'Orbigny, for T. concentrica, &c. ; and claims the priority of his genus Merista, 

 for M. Herculea, M. scalprum, and other similar species. Mr. S. P. Woodward adopts Athyris, as 

 originally defined {A. concentrica), , 5 and, the sub-genus Merista, Suess, for T. Herculea, T. scalprum, &c. 



1 M. Suess' speculation touching the use of the pores in the apparatus of Thecidium vermiculare, is per- 

 haps hazardous. 



2 * A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland,' p. 87, pi. xix, 

 fig. 7, 1844. 



3 Suess, in p. 58, of Leonhard's ' Neuves Jahrbuch,' Jan., 1854. 



4 Described by M. Suess, under that denomination, in the 'Jahrb. d. k. Geol. Reichs-Anstalt,' ii, 

 iv, 150, 1851 ; and again mentioned in Leonhard's 'Neuves Jahrbuch,' p. 127, 1854. 



5 'Manual of the Mollusca,' part ii, p. 244, 1854. 



