. ADDENDA. 



Aparchites, Jones. 



minutissimns [Hall] Ulrich, 1889 ; Contributions Micro-PaL-eont., part 2, 

 p. 49, Trenton and Hudson River. 



For other references see Leperditia [Isochilina} minutissima. Hall, 

 unicornis, Ulrich, 1889 ; id., p. 50, plate 9, fig. 11. Hudson River. 



For other references see Leperditia unicornis, Ulrich. 

 Bythocypris, Jones. 



cylindrica [Hall] Ulrich, 1889 ; id., p. 48, plate 9, fig. 6. 



Trenton and Hudson River. 

 For other references see Leperditia {^Isochilina'] cylindrica, Hall. 

 Eurychilinda, Ulrich. 



Valves semicircular, suboval, or even nearly circular. Dorsal line 



straight, generally with a well-defined sub-central sulcus and a more 



or less prominent node just behind it. A very broad convex border 



• extends around the valves from the antero-dorsal to the postero-dorsal 



angle. The border is often striated in a radial manner, and in most 



cases terminated by a marginal "frill," or by a plain narrow border, 



usually directed slightly outwards. The main body of the border, 



however, curves inward to near the plane of contact between the two 



valves, thus forming a deeply concave outer area. Hingeraent simple. 



Surface reticulate, granulose or smooth. 



reticulata, Ulrich, 1889 ; Contributions Micro-Palaeont., part 2, p. 52, 



plate 9, figs. 9 and 9 a. Trenton. 



Manitobensis, Ulrich, 1889 ; id., p. 53, plate 9, figs. 10 and 10a. 



Hudson River, 

 striato-marginata [Miller] Ulrich, 1889 ; id., p. 52. 



For other references see Beyrichia striato-marginata, Miller. 

 Leperditia subcylindrica, Ulrich, 1889 ; id., p. 49, plate 9, figs. 4-4 b. 



Trenton and Hudson River. 

 Primitia lativia, Ulrich, 1889 ; id., p. 50, plate 9, figs. 8, 8 a. Hudson River. 

 ?[? Beyrichia] parallela, Ulrich, 1889 ; id., p. 51, plate 9, figs. 7-7 a. 



Hudson River. 



Strepula, Jones & HoU. 



lunatifera, Ulrich, 1889 ; id., p. 56, plate 9, figs. 14-14 b. Hudson River, 

 quadrilirata [Hall & Whitfield] Ulrich, 1889 ; id., p. 54, plate 9, fig. 12. 



For other references see Beyrichia quadrilirata, Hall & Whitfield, 

 quadrilirata, var. simplex, Ulrich, 1889 ; id., p. 55, pi. 9, fig. 13. 



Prof. Ulrich's article has appeared while this paper was going through the 

 press ; as therefore it was impossible to embody these references in the main 

 text, they are added here. 



