136 PERMIAN FOSSILS. 
Genus Athyris' (partim), M‘Coy, 1844. 
AtryPA (partim), Dalman. 
SprriceRA, A. d Orbigny, 1848. 
Typified with Von Buch’s Zereératula concentrica,’ this group is characterised with 
an internal structure widely removing it from its immediately associated genera. In my 
paper on the ‘ Palliobranchiata,’ it was shown that the apophysary system of the last- 
named shell possesses a peculiar character.’ The dental plates are not immediately 
attached to the imner surface of the large valve, as in Cleiothyris, but to a singular 
structure resembling, when detached, a shoe-lifter, and cemented by its lateral margins 
to the medio-longitudinal region of the valve, with the narrow end fitting into the 
point of the umbone, and the opposite end terminating over the centre of the shell. 
The small valve is furnished with an elevated medio-longitudimal plate, supporting the 
crural base. Mr. ‘I’. Davidson has more recently published some figures representing 
the interior of Atrypa tumida, Dalman,* which I am led to believe belongs to the 
present genus. In examining my own specimens of this species, from Norway, with 
the view of ascertaining if it possessed an apophysary system resembling that of 
Athyris concentrica, 1 have discovered in the small valve precisely the same largely- 
developed medio-longitudinal plate supporting the crural base as in the latter: the 
shoe-lifter-like process, however, only exists under a rudimentary condition. But in 
a large specimen of an allied shell (if not a variety) found at Malvern, and evidently 
the same as the one identified by Mr. T. Davidson with Dalman’s species, the last 
structure is more decidedly developed. The convex body between the dental plates 
in one of Mr. Davidson’s figures, already noticed, appears to be the structure alluded 
to. A shoe-lifter-like process is to be seen in the Zerebratula Herculea of M. Barrande 
as well developed as in Athyris concentrica. I forego making any further remarks on 
the internal structure of this genus; because it is understood that M. Bouchard 
Chantereaux is in possession of some novel and excellent materials which he is 
preparing for publication. 
Should Atrypa prunum, Dalman, hereafter prove to be a species of Athyris, which 1 
confidently anticipate, this genus will be placed in immediate proximity to Martina ; 
since the species just named, by its form and rudimentary area, is closely related to 
Martinia pachyrhynchus, De Verneuil ; while in another point of view A¢hyris is without 
doubt proximately connected with the following. 
1 The name Athyris, like Atrypa, is a misnomer ; as few, if any, of the species are without a foramen. 
2 T suspect that Terebratula concentrica, Von Buch, is the only species of the number placed by M‘Coy 
in Athyris, belonging to the genus: all the others appear to belong to Cleiothyris. 
3 Vide Annals and Magazine of Natural History, vol. xviii, p. 86, 1846. 
4 Vide Bull. de la Soc. Géol. de France, 2™° serie, t. v, pl. iii, fig. 26. 
