TRENTON CONGLOMERATE OF RYSEDORPH HILL 83 



The flat body of the valve, the u-shaped ridge and the (marginal 

 ridge are all characteristic features of the genus Bollia, but, 

 while one or both ends of the loop-shaped ridge may be bulbous 

 in that genus, no species known to the writer presents such a 

 great difference in the development of the two ends of this ridge, 

 nor is the marginal ridge usually situated so closely to the 

 margin as it is in this species. 



MACRONOTELLA Ulrich 



Macronotella ulrichi sp. nov. 

 PI. 6, fig. 6-16 

 In the gray crystalline limestone pebbles of the conglomerate 

 at Rysedorph hill and the Moordener kill (pi. 7, fig. 1) occur 

 representatives of the genus Macronotella known only by 

 one species from the Lowville limestone of the west. This genus 

 is characterized by Ulrich as follows: " Carapace convex, semi- 

 circular or semiovate, with a long nearly straight hinge; valves 

 equal, full centro-dorsally, without ridges or a sulcus, but exhibit- 

 ing a smooth subcentral spot where the ornament is omitted; 

 surface, in the only species known, coarsely punctate." The 

 affinities of the genus are thought to be with Kifkbya. In 

 the conglomerate beds two species have been found, which are 

 distinctly allied to Macronotella scofieldi, the type of 

 the genus. 



Diagnosis. Valves three fourths circular to subovate; dorsal 

 outline rarely straight, mostly prominent in the central part, 

 specially in older specimens; cardinal angles obtusely rounded to 

 shortly truncate; posterior margin with a little longer truncation, 

 lateral and ventral margins forming approximately a continuous 

 circular line, in larger specimens the anterior and posterior mar- 

 gins more strongly rounded, and the ventral margin less curved; 

 free edges in most specimens with a broad depressed border and 

 beveled edge. Surface strongly convex, culminating in the dorso- 

 central region; in some specimens almost smooth, with only faint, 

 widely and irregularly distributed circular impressions; others 



