EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA I 73 



name it is necessary to state the value which we assign to this term. After 

 the introduction of Conrad's name Vanuxem appHed the term A try pa 

 singularis to a species from the Helderbergian fauna and in volume 3 

 o{ \\\it Palaeontology of Nciv York Professor Hall recognized both species, 

 stating that he had found both in the Helderbergian but only A. (E a t o n i a) 

 peculiar is in the Oriskany. Hall admitted the very close similarity in 

 these species but found the distinguishing difference in the broader outline 

 ofE. singularis, the more elongate form of E. p e c u 1 a r i s . He said: 



This species was regarded by Mr Conrad as restricted to the Oriskany 

 sandstone; but in the course of many years' collections, a considerable 

 number of specimens have been found in the limestone of the Lower Helder- 

 berg group. In its surface characters, it scarcely differs from the preceding 

 species ; the form, however, is always more or less distinctly ovate ; the 

 mesial sinus less deeply and less distinctly pronounced ; while the mesial 

 fold of the opposite valve is less abrupt, and does not extend so nearly to 

 the beak of the valve ; the margins of the valves, and particularly of the 

 ventral valve, are distinctly inflected along the cardinal slopes, giving an 

 undefined oval area on each side below the beaks. The crenulations in 

 front are always visible in well preserved specimens, and these sometimes 

 produce a slight undulation or plication of the exterior near the margins. 



While these differences are marked in the New York shells to such a 

 degree that they may always be observed, yet in the New York Oriskany 

 there are shells both of the broad and of the elongate type. In view of the 

 fact that no other distinction has been admitted and that none are palpable 

 it is clear that tlie shells have been artificially separated. Yet there is a 

 certain value attaching to the difference noted. The broad form prevails 

 in Helderbergian faunas of New York, it is about equally present with the 

 elongate form in the New York Oriskany while the latter is the prevalent 

 if not the exclusive shell in the Cumberland (Md.) Oriskany. In Gaspe 

 the shells are all of the broad or singularis type, retaining throughout the 

 fine sgraffito radial ornament of the shell and the usual predominant median 

 stria ; they are moreover a wholesome vigorous race attaining commonly a 

 size which is noteworthy in comparison with the New York and Maryland 

 shells. They are strongly contrasted with the small and elongate New 

 York shells of E. p e c u 1 i a r i s , with their narrow tongue-shaped extension 

 of the sinus. This large type of shell is rarely present in the Glenerie 

 Oriskany. Myriads of smaller shells compose some of the rock layers, but 

 between large and small there are no specific distinctions, and none that 

 are not easily overpassed between these and the most extreme forms of E. 

 p e c u 1 i a r i s . These relations are thus expressed : 



