112 DESMIDS OF THE UNITED STATES. 



Var. REDUCTUM, Nord. Plate XXX, fig. 3. 



This specimen does not agree as well as many others found 

 in the same locality and group. I therefore add a transla- 

 tion of the author's diagnosis from his De Algis Musei 

 Lugduno-Batavi : 



"Sinus between the semi -cells linear; sides and angles 

 close ; end lobe scarcely dilated, apex retuse, middle lobe 

 small ; end view rectangular ; tumor in the middle of the 

 semi-cell obovate elliptic, others very small." 



E. CIRCULARS, (Haas.). Ralfs - Plate XXXII, figs. 1, 2. 



Semi-cells three-lobed, mostly with three basal tubercles ; 

 end notched, scarcely dilated. 



Ealfs makes three varieties : a. semi-cells inflated at the 



base and attenuated upwards ; b. semi -cells emarginate at 



the sides, the basal portion with five tubercles : c. emarginate 



at the sides ; tubercles smaller, more numerous and scattered. 



Diameter 36 /*., more or less. 



Rhode Island, Pennsylvania, New Jersey ; common. 



E. GEMMATUM, Breb. Plate XXXII, figs. 3, 4. 



About one-half longer than broad ; semi-cells three lobed, 

 lateral lobes horizontal, deeply emarginate: the protuber- 

 ances minutely granulate ; terminal lobe dilated, broadly 

 emarginate; transverse view broadly elliptic, with three 

 granulate inflations on each side (not four, as incorrectly 

 drawn) and one at each end ; end view shows the terminal 

 lobe, cruciform. 



Diameter 38 yw. 



Found from Rhode Island to Minnesota, and southward. 



E. EVERETTENSE, Wolle. Plate XXXII. figs. 5, 6, 7. 



Cells about twice as long as broad ; semi-cells three lobed, 

 basal lobes wide, emarginate; end lobe dilated, notch linear; 

 two larger inflations near the middle, and several smaller 

 ones on each side, and on end lobe. Transverse views 

 broadly elliptic, with two protuberances on each side ; side 

 view shows one inflation on each side. 



Diameter 50-55 ju. 



Collected in pond*, Mount Everett, Mass. 



This form bears some resemblance to E. ftfflne, but it is 

 clearly separable by the broad basal lobe, by the absence of 

 the intermediate prominences, and by the arrangement of the 

 protuberances which produce distinct forms in transverse and 

 lateral views. 



