I08 Clarence J. Elmore 



Cleve; GomphoncUa Rabenh. ; SpJicHcIla Kiitz.; Sphenosira 

 Ehr. 



Etym., from Gr. yo>0os, wedo-e. and vniJ-a, thread, the plant hav- 

 ing the appearance of a wedge borne on the end of a thread. 



Cells single, mostly stalked, or in gelatinous masses, cimeate in 

 both girdle and valve views ; interzones present ; valves bilaterally 

 symmetrical, often with one or two constrictions; raphe straight 

 with central and terminal nodules ; surface transversely punctate- 

 striate, the striations sometimes lacking opposite the central nodule, 

 giving the appearance of a stauros. Chromatophore one large 

 plate lying next to the girdle. Auxospores two from two mother 

 cells in a common gelatinous envelope. 



A. With an isolated dot on one side of the central nodule. 



b. Median striations alternately long and short. i. G. constrictum. 

 bb. Median striations not alternately long and short. 

 c. Without stauroneiform area. 

 d. Not lanceolate-rostrate. 

 e. Upper apex apiculate. 



/. Gibbous in the middle. 2. G. acuminatum, 



ff. Not gibbous in the middle. 3. G. augur, 



cc. Upper apex not apiculate. 



/.Upper apex broadly rounded. 



g. With rows of dots between the striations. 



4. G. herculcanum. 

 gg. No dots between' the striations. 



5. G. ericnse. 

 ff. Upper apex not broadly rounded. 



g. Striations coarsely punctate. 



6. G. lanceolatum. 

 gg. Striations not coarsely punctate. 



h. Striations 7 or more in 10 ^ ; ventral area 



. narrow. 7. G. montanum. 



hh. Striations fewer than 7 in 10 m ; ventral 

 area broad. 8. G. validum. 



dd. Lanceolate-rostrate. 



c. Middle area round. 9. G. parvulum. 



ee. Midd'.e area on one side of the central nodule. 



ID. G. aitgustafu))!. 

 cc. With stauroneiform area. 



d. At least one end of the valve acute. 11. G. gracile. 

 dd. Both ends nearly equally obtuse. 12. G. intricatum. 



