146 Clarence J. Elmore 



Etym., from Gr. o-^iyyetV, to bind, and kwtis, cell, the species to 

 which the name was first applied being constricted in the middle. 



Cells free, oblong to linear, straight ; valve surface undulate and 

 transversely striate with a beaded keel on each margin containing 

 the raphe ; a straight pseudoraphe along the center of the valv.e. 

 Chromatophores two plates lying next to the valves. Auxospore 

 one from two cells. 



A. Broadly elliptical or elliptic-lanceolate. i. S. clliptica. 



AA. Linear with apices usually rostrate. 2. 5". librilis. . 



1. Sphinctocystis elliptica (Kiitz.) Kuntze. Rev. Gen. Plant., 



Ill, p. 431. 1898. 



Cymatopleura clliptica (Kiitz.) W. Sm. in Ann. and Mag. A^at. 

 Hist., p. 133. i8§i. 



Surirclla clliptica Kiitz. Bacill., p. 61, pi. 28, fig. 28. 1844. 



PI. 20, fig. 778. 



Elliptical or elliptical-lanceolate, sometimes slightly constricted 

 in the middle, 70-140 /a long, marginal costae short, resembling 

 beads, 3-4 in 10 /x; striations delicate, about 18 in 10 /x; valves 

 undulate, showing 4 or 5 depressions. The spiral form mentioned 

 by Wolle, Diat. of N. A., pi. 108, fig. 6, occurs quite commonly 

 mixed with the normal form and is evidently only an abnormal 

 form of it. It is found also in fossil material from Mullen. 



In creeks, rivers, ponds, springs, etc., usually where conditions are es- 

 pecially favorable for algae, also fossil : Broken Bow, Callaway, Central 

 City, Crawford, Fremont, Grand Island, Julian, Nemaha City, New Helena, 

 North Platte, Orleans, Plattsmouth, Ruby, St. Paul, Seneca, Talmage, 

 Thedford, Valentine, Wann, Weeping Water. 



Fossil : Hay Springs, Mullen, Valentine. 



Blackpipe, Little White River, Rapid City, Rosebud, S. Dak. ; Cheyenne, 

 Wyo. ; Stockton. Cal. ; Emporia, Kansas. 



2. Sphinctocystis librilis (Ehr.) Hass. Brit. Freshw. Alg., p. 



436, pi. 102, fig. 3. 184^. 

 Naviciila librilis Ehr. Inf., p. 76*5. 1838. 

 Cymatopleura solca (Breb.) W. Sm. in Ann. and Mag. Nat. 



Hist., p. 12, pi. 3, fig. p. 18^1. 

 Surirclla solca Breb. Consid., p. ly. 1838. 



