160 DESMIDS OF THE UNITED STATES. 



and others in its more slender cell, and in the larger number 

 of umbonations. Cell twenty or more times longer than 

 broad, medianly distinctly constricted, without an evident 

 suture or projecting rim. Semicells tapering Blightly, in 

 direct lines from the centre to the end, with not only one or 

 two inflations (umbonations) at the base, but four, live or 

 more, often extending in slight undulations to near the end ; 

 apex squarely truncate, bordered by three to five minute 

 tubercle-. 



Diameter 16-20 /*.; length 300-400//. 



Euastbum ventricosum, Lund. (Add to page 97). 



Without a figure tor Illustration, this species may be most 

 satisfactorily described by comparison with E. crassum, Kg., 

 to which it i:- very nearly allied, and in front view scarcely 

 separable excepl in size; it has only about halt' the length of a 

 fully developed, large form ; it i- more squatty, less than twice 

 as long as wide; in lateral view, however, it is quite distinct ; 

 semicells not ovate, with convex sides, narrow truncate end, 

 and broad flat base, but subrectangular ; end broad, flatly 

 rounded; sides somewhal contracted near the apex, producing 

 a lobule on each side; another lobule on each side between the 

 base and the apex ; each of the superior lateral lobes Been in 

 front view , when seen from the side, -how an obtusely rounded, 

 conical point near tin' apex, not bifid as in E. crasmm. The 

 end view varies also; it is broadly elliptic, with four, or im- 

 perfectly, five swellings on each side, not three. 



Diameter 50 ".. ; length 88 u. 



Frequent with zygospores, which are orbicular, furnished 

 with numerous, short, stout, obtusely pointed, conical tuber- 

 cles ; two, often converging, or diverging, the one to, or from 

 the other. 



A. Incus, Qass. (Add to page 97). 



A variety from lakes, Winter Park, Florida, which differs 

 from the forms figured in having the ends of the semicells 

 somewhat convex, the side- not rounded hut gibbous near the 

 base; sinus wide, internally rounded; spines converging. 



