84 NEW YORK STATE MUSEUM 



with very large deep pits; on the apex always a flat, smooth 

 circular area. Valve projecting slightly above the straight car- 

 dinal line, and forming a broad, low, triangular, reentrant car- 

 dinal area. 



Dimensions. Length 2.7 mm; hight 2.1 mm; thickness .7 mm. 



Horizon and locality. In the gray crystalline pebbles of the 

 conglomerate on Rysedorph hill and at the Moordener kill. 

 (Group 7) 



Observations. This pretty species agrees with the type of the 

 genus Macronotella in its convex valves, culmination in the 

 dorso-central region, apical smooth spot, border and coarse punc- 

 tation; it differs in being relatively much shorter and haAing a 

 shorter cardinal line; it also has obscure or truncate cardinal 

 angles. It api>ears that the definition of the genus should be so 

 modified for the reception of this and the next species, as to 

 embrace forms of not only long but also of relatively short hinge 

 line. 



This form shows a slight similarity to a round, punctate species 

 with beveled border and dorso-central apex, from Scandinavian 

 upper Siluric beds, described by Jones as Aparchites 

 decor atus.^ The Swedish form does not apparently possess 

 the apical smooth spot and has a very short cardinal line; its 

 reception into the genus Macronotella would therefore be not 

 advisable. 



Another si>ecies which may be mentioned in this connection, is 

 Isochilina amii Jones,^ from the Trenton limestone of 

 Loretto, province of Quebec. This species is described by Prof. 

 Jones as follows: "A small black valve, ovate oblong; dorsal 

 border long and straight; anterior end evenly and posterior one 

 elliptically rounded, ventral edge nearly curved and obscurely 

 crenulated. Surface marked with small scattered pits; greatest 

 convexity at the hinder moiety." It is added: "This seems to 

 ditfer from nil known forms. It has the Lei)erditian shape of 

 Isochilina, although no sulcus nor tubercle is visible." There 



* An. and mag. nat hist 1889. p. 272. 



• Oontrlb. Cata. ralcro.-pal. 1891. pt3, p. 68, pi. 10, fig. 14. 



