l-M> PERMIAN FOSSILS. 



Genus Athjris^ {partim), M'Coy, 1844. 



Atryi'a {partim), BaJman. 

 Spirigera, a. d'Orbigny, 1848. 



Typified with "V'on Buch's Tercbratuin concentrica^ this group is characterised with 

 an internal structure widely removing it from its immediately associated genera. In my 

 ])aper on the ' Palliobranchiata,' it was shown that the apophysary system of the last- 

 named shell possesses a pecahar character.^ The dental plates are not immediately 

 attached to the inner surface of the large valve, as in Cleiotlujris, 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 

 j:)oint of the umbone, and the opposite end terminating over the centre of the shell. 

 The small valve is furnished witli an elevated medio-longitudinal plate, supporting the 

 crural base. Mr. T. Davidson has more recently published some figures representing 

 the interior of Atrypa titmlda, 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 

 Atlif/ris concenirica, I have discovered in the small valve precisely the same largely- 

 developed medio-longitudinal plate supporting the crural base as in the latter : the 

 shoe-liftcr-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 

 tlie 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 Terehratuhi llerculea of M. Barrandc 

 as well developed as in Athjris concentrica. I forego making any further remarks on 

 the internal structure of this genus ; because it is understood that M. Bouchard 

 Chaatereaux is in possession of some novel and excellent materials which he is 

 preparing for publication. 



Should Atrppa prunum, Dalman, hereafter prove to be a species oi Athyris, which I 

 confidently anticipate, this genus will be placed in immediate proximity to Martinia ; 

 since the species just named, by its form and rudimentary area, is closely related to 

 Martinia paclit/rhynchus, De Verneuil ; w^hile in another point of view Athyris is without 

 doubt proximately connected with the following. 



1 The name Atlnjris, like Atrypa, is a misnomer ; as few, if any, of the species are without a foramen. 

 - I suspect tliat Terehratula concentrica, Von Buch, is the only species of tiie number placed byM'Coy 

 in AtJtyris, hclonging to the genus: all the others appear to belong to Cleiothyris. 

 ^ Vide Annals and Magazine of Natural History, vol. xviii, p. 86, 1846. 

 ^ Vide Bull, de la Soc. Geol. de France, 2""" serie, t. v, pi. iii, fig. 26. 



