86 INTRODUCTION. 



appellation, selecting for that purpose Cleiothyuis of Phillips,^ but not exactly in the 

 sense intended by that author. It however so happens that the true T. concentrica and 

 T. pedinifera, although different species, are essentially similarly organised, and belong to 

 the same group, while on the other hand. Professor King's so-called Athyris concentrica 

 possesses the characters of another section, of which A. tumida (Dal.,) or T. Herculea 

 of Barrande, may serve as types. If we preserve Professor M'Coy's misnomer, Athyris, 

 for T. concentrica, another name would be required for those species possessing the 

 shoe-lifter process described by Professor King, but which have been united into the same 

 group, both by M. d'Orbigny, Professor M'Coy, and others. On perusing the last-named 

 author's recent publication,^ I find therein a slight but important modification in the 

 description of Athyris, viz., " a stro?iy mesial septum exists in the rostral portion of the 

 entering valve; dental lamella are moderate; no foramen." Example, A. tumida, Dal. 

 Such a diagnosis could in no way answer to T. concentrica, while, on the contrary, it quite 

 agrees with the state of things observable in the group characterized by A. Tumida"^ and 

 Herculea. I therefore think that it would be preferable to retain for the last-named 

 species and similar forms with an apparently imperforate beak or closed foramen, variously 

 disposed septa, and largely developed dental plates, the term Athyris, M'Coy; and to adopt 

 for those forms similar to T. concentrica, pectinifera, Roissyi, &c., the name Spirigera, 

 D'Orb., by which means the palpable misnomer of Professor M'Coy is partially got rid of, 

 and the name Athyris still retained for shells more closely partaking of the author's diag- 

 nosis and intentions.'' The species belonging to this section are easily distinguished ex- 

 ternally from Spiriyera by a longitudinal line, which extends along the smaller valve from 

 the umbo to half or more of its length, and which denotes the presence of the internal 



^ A Mon. of English Permiiin Fossils, p. 137, 1849. Professor Phillips proposed the name Cleiothyris 

 as a substitute for Dalraan's Atnjpa, but did not employ it in his work, ' Fig. and Desc. of the Pal. Fossils 

 of CornwaU, &c.,' p. 55, 1841. 



2 British Pal. Foss. in the Camb. Mas., p. 196, 1852. 



^ It is worthy of notice that Sowerby was the first author who described and figured the exterior and 

 spires in this species, under the name of T. ohtusa, and which denomination seems to hold priority over that 

 oi tumida, given to the same species by Dalman in 1827. — See Sowerby; Some Account of the Spiral 

 Tubes or Ligament in the Genus Terebratulu of Lamarck, &c., read in 1815, and published in vol. xii of 

 the 'Trans, of the Linn. Soc of London,' p. 515, pi. xii, fig. 3, 4. 



* Before coming to the above conclusion, I submitted my views to M. Deshayes, Mr. Salter, and 

 others, who seemed to consider that this mode of compromising the difficulty could not reasonably be 

 objected to by the two authors principally concerned, nor by the generality of Palaeontologists. I have 

 always been of opinion, that if a name implies a radical zoological error it should be expunged, as the great 

 object of science is to improve the nomenclature, and not to endeavour io perpetuate an error, even on the 

 grounds of priority. 



I must not omit to observe, that there exists a slight difference in the interior of A, tumida and 

 herculea from the shoe-lifter process, assuming only a rudimentary state in the first species ; but it seems 

 to possess all the other essential characters of the genus, and I therefore agree with Professor Ring who 

 proposes to place them both for the present into the same section. 



