250 NEW YORK STATE MUSEUM 



itive expression and that here concerned an intermediate stage. 

 Regarding the last named this condition is evinced in a usually 

 greater thickening of the hinge plate than prevails in Beachia, 

 and a less strong development of the muscular scars than in 

 M. o V a 1 i s . 



B. suessana is an Oriskany species of the Cumberland basin, 

 Maryland. The specimen which has been identified therewith in 

 the Oriskany at Rondout is familiar to the writer but there is no 

 particular reason for assigning it to Beachia rather than to Meg- 

 alanteris. The simplest expression of these shells is therefore the 

 most southerly. 



For the sake of an expression therefore the term applied to this 

 species will serve. It is evident that the generic distinction be- 

 tween Beachia and Megalanteris is a fugitive one and of little 

 value. Probably it will be found wise to withdraw the former 

 term altogether and express the relations here indicated by specific 

 terms which are even then too exacting. It is not a matter of 

 record that these species have the same character of brachial 

 processes but specimens are before me from the Glenerie Oriskany 

 which show this to be the case. 



Lower Devonic. Grande Greve and Perce rock, P. O, 



Megalanteris thunii nov. 



Shells having the aspect of M. o v a li s Hall often with more 

 convex ventral valve and distinguished chiefly by numerous gen- 



9 



Megalanteris thunii 



erally fine radial plications covering the entire surface except the 

 umbones. This last feature is highly developed and is not con- 

 nected by gradation with the smooth exterior of M. o v a li s. 



