EARLY DEVONIC HISTORY OF NEW YORK AND EASTERN NORTH AMERICA 123 



Leptostrophia magnifica Hall protype parva Clarke 



Plate 31, figures 5-9 

 Sfe pt i, p. 190 



Leptostrophia magnifica Hall var. parva Clarke. N. Y. State Mus. Bui. 107. 

 1907. p. 274 



This shell may be best expressed in terms of the widespread L . p e r- 

 p 1 a n a Conrad and L . b 1 a i n v i 1 1 i i Billings, for it approaches these in 

 all general features. 



1 The surface striae, fine, threadlike and crowded, exhibit some diver- 

 sity of size in early growth and this becomes intensified later so that about 

 the margins there is either an inclination to irregular swelling or to fascicu- 

 lation, the latter at times being quite pronounced. These are characters of 

 L. magnifica not of L. perplana. Concentric wrinkles on the 

 shell are altogether absent. 



2 The cardinal area is denticulate to its extremities though narrow and 

 but slightly cross striated ; the delthyrium is open. 



3 The muscle scars are not greatly divergent but, as in L. mag- 

 nifica, are contracted at the beginning though they extend more than 

 halfway across the shell. 



The shell is essentially a diminutive expression of L. magnifica, its 

 fundamental structure being quite in harmony with it and its lesser variety 

 tardifi from the Perce rock. In our material an occasional specimen 

 indicates the presence of individuals larger than these we have figured. 

 Dr Drevermann, after examination of these specimens, finds this shell closely 

 approaching L. explanata Sowerby of the Coblentzian though that 

 shell attains more nearly the dimensions ofL. magnifica and has flatter 

 rather than threadlike striae on the surface. 



Locality. Edmunds Hill. 



When we undertake a comparison with the Leptostrophias of the early 

 Devonic which we have here considered, L. magnifica Hall (Oriskany 

 and Grande Greve), L . magnifica tullia Billings (Perce"), L. tardifi 

 Clarke (Perce), L. magnifica parva Clarke (Chapman Plantation) 

 with the prevailing Leptostrophia of the Coblentzian, L. explanata 

 Sow., it is evident that we are dealing with essentially like quantities. It 

 would be less difficult to express the last named in terms of any one of the 

 others than in terms of them all. The original figure of this species [Geol. 

 Trans. 2 ser. 1842, v. 6, pi. 38, fig. 15] is the clearest possible expression 

 of the ventral interior of a rather small form of L. magnifica, hence 

 of var. tullia or practically var. parva. That the species attains 

 greater dimensions and broader muscle scars is evinced by Schnur's ' and 



'Bracli. d. Eifel, pi. 39, fig. 6. 



