R. Ethendge, Jim. — On Carboniferous Mollusca. 153 



towards the posterior side. Posterior ears undefined from the body 

 of the shell, variable, rectangular or a little pointed, but not extending 

 beyond the posterior margin. Anterior ear of the right valve long 

 and narrow, well divided from the body of the shell by a narrow 

 notch extending nearly to the beak ; anterior ear of the left valve 

 obtusely rounded, with a slight notch in its margin. Hinge line 

 nearly equal to the width of the shell ; greatest height obliquely 

 from the beaks to the postero-ventral margin. Beaks small, surface 

 covered with irregular, unequal, flattened radiating ridges frequently 

 bifurcating, separated by flattened spaces of unequal breadth, and 

 crossed by concentric scale-like strias or lamina usually stronger on, 

 and near, the ears; the ridges increase in size towards the ventral 

 margin, and are supplemented by the interpolation of additional ones 

 which do not extend as far as the beaks. Ears ornamented in a 

 similar manner to the shell. 



Ohs. — Amongst individuals of A. papijraceus there appears to be a 

 certain amount of variation. Sowerby's figures show no separation 

 of the ears from the shell, but this is perhaps due, as Prof. McCoy 

 has pointed out, to the state and mode of preservation of the speci- 

 mens. Prof, de Koninck has figured an example of the left valve in 

 which the anterior ear is acutely pointed. Dr. Goldfuss has figured 

 a right valve with a short anterior ear. Prof. McCoy remarks on 

 the smaller size of the anterior ear of the right valve, and states 

 that it is separated from the body of the shell by a deep narrow 

 notch extending to the beak, which is the usual aspect of British 

 specimens. In Mr. Salter's figure, apparently a left valve, the 

 anterior ear is not at all separated from the body of the shell, and the 

 posterior ear is almost rectangular, although this is of less moment, 

 as Prof, de Koninck states that the posterior margin is usually 

 rectangular, but sometimes sinuous. Under these circumstances I 

 believe I am justified in regarding the figured specimen as a variety 

 of A. jpapyraceus, of which it possesses the characteristic ornamen- 

 tation and form. Unfortunately the anterior ear of the right valve 

 is not entirely preserved, although it is clear that it was long and 

 narrow, but apparently not quite so separated from the body of the 

 shell as it should be. From A. subpap^jracea, de Yern. et de Key.,^ 

 it is distinguished by the shortened hinge line, rounded posterior 

 end, and much less number of radiating ridges of the latter species, 

 although the ridges are said by Counts de Verneuil and Keyserling 

 to be dichotomous. In its posterior obliquity and general characters 

 the shell at present under consideration resembles A. Neptuni, Goldf.,- 

 A. granosus, Sow.,^ and A. plicatiis, Sow.,"^ more especially the last 

 named, but may be distinguished by the peculiar and decided trun- 

 cation of the shell, by the hinge line, larger ears, especially the 

 posterior, and the more complex nature of the ornamentation. 

 Irrespective of other characters, the granulation of the radiating 

 costse in A. granosus is sufficient to distinguish the latter from 



^ Murchison's Eussia, vol. ii. p. 325, t. 21, f. 3. 



- Petrefacta Germ. vol. ii. p. 125, t. 116, f. 4. 



3 Min. Con. vol. vi. p. 144, t. 574, f. 2. * I.e. t 3. 



