238 



NEW YORK STATE MUSEUM 



Rensselaeria ovoides Eaton (sp.) var. gaspensis nov. 



Analyzed as to exterior characters this shell is a miniature of 

 the great R. o v o i d e s of the New York Oriskany, varying in 

 proportion, dimensions, outline and convexity, much as that shell 

 does, that is, frequently high-shouldered and broad across the 

 umbones, rarely broadest in the pallial region, often with lateral 

 margins vertical or slightly introverted specially about the umbones, 

 but as often without this character, usually with the ventral valve 

 medially elevated, and finally with a diversity in the character of 



Rensselaeria ovoides var. gaspensis 

 Left hand figure, Gaspd sandstone; central, Grande Greve; right hand, Perc^ 



surface striation which is due to the fact that the fine striae of 

 early age maintain their simplicity but increase in width without 

 additions, to that in old shells or progressed stages of relatively 

 young shells where the surface may seem to be coarsely marked. 

 On the other hand the shells are characterized by a prevailing 

 narrow elongate-linguate outline with parallel lateral margins for 

 a great part of their length. On the interior there are few notable 

 and perhaps no constant differences, whether in respect to structure 

 of musculature or cardinal plate. It is, however, here important 

 to bring forward the fact which the writer has already expressed 

 with some emphasis, that as between the genera Rensselaeria (as 

 based on the type species R. ovoides) and its chronologic suc- 

 cessor Amphigenia, there is a distinction solely in one structural 



