COSMARIUM. 69 



merging, concave ; ends truncately rounded ; membrane punc- 

 tate ; end view oval. 



Diameter 28-31 ft. 



Pond.s, Pennsylvania, rather rare 



Scarcely separable from a variety ti L r . 28 of < '. Holmiense, 

 except by the punctate membrane and the usually wider sinus ; 

 the hitter is not correctly represented in fig. _''_', should be 

 two or three times wider and not (|uite so deep. 



C. pyramidatum, Breb. Plate XIV, figs. 1'>, 17. 



Cell scarcely twice as long as broad, suboval ; constriction 

 deep, linear ; semicells pyramidal, rounded at basal angles, 

 sides convex, gradually converging to the somewhat truncate 

 ends; punctate; end view broadly elliptic. 

 I tiameter 50- 85 y. 



A commoD Bpeciea Pound probably in every State of the 

 Union. 



Var. stenonotum, Nord. Plate XIV, figs. 18, 19. 



This subspecies is separated from the typical form by the 

 shape of the sides of the semicells, which are somewhat 

 retuse near the apices ; for perfect identity the ends ought not 

 to be retuse ; my specimens are slightly concave. 



Size about the same as the typical plant. 



Found this variety in collections made by Mi E. Under, 

 Minneapolis, Minnesota, and by A. I). Balen, Plainfield, 

 N< u Jersey. 



< '. P8EDDOPYRAMIDATUM, Lund. Plate XV, figs. 11, 1-. 



In habitat, in form and proportions like the true plant, but 

 only about halt' the size. It corresponds \\ ith < '. pyramidatum, 

 variety minus. Reinsch; Rab. AJg. Exsic. No. 1902. 



Besides these, Ralfs ha- a Forum major, which I have in- 

 cluded in my general grouping, iti'_r. 17). 



( '. Kai.fsii, Breh. Plate XV, fig. 1. 



Orbicular or suborbicular, deeply constricted, sinus narrow 

 lineai- ; semicells nearly semicircular ; interior angles obtuse, 

 dorsum high convex ; cytioderm smooth or finely punctate, 

 Diameter 60-100 ".; length 70-120 <l 



