124 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



SURIRELLA TURPIN (1828) 



(named after Dr. Suriray, a physician of Havre) 



Valve linear, elliptical or ovate; pseudoraphe linear or lanceolate; a marginal keel 

 forming wings or ate seen in zone view; costse short or reaching the pseudoraphe, frequently 

 with intercostal strise more or less evident. 



The genus is divided by Grunow according to the length and form of the costse. 

 I include Stenopterobia. 



Section 1. Costse of nearly equal width throughout, reaching the pseudoraphe. 



Section 2. Costse short or marginal. 



Section 3. Costse dilated at the margin, attenuated toward the pseudoraphe. 



Section 4. Valve having the appearance of Nitzschia, with inconspicuous alse 

 (Stenopterobia). 



The endochrome consists of two laminate chromatophores, one on each valve. 



The auxospores are single, originating from the union of two frustules (H. L. Smith). 



SECTION 1 



SUKIRELLA BISERIATA (EHR.) BREB. 



Valve lanceolate, subacute at the ends; costse robust, about 2 in 10 n, parallel in the 

 middle, radiate at the ends; pseudoraphe narrow. L. 100 n. 

 Surirella bifrons Ehr. 

 Fresh water. 

 PI. 39, Fig. 12; PI. 35, Fig. 2 (smaller form). 



SURIRELLA LINEARIS WM. SM. 



Valve linear, with cuneate ends, slightly constricted in the middle; costse parallel, 

 2-3 in 10 p. L. 90 ju- 

 Fresh water. 

 PI. 35, Fig. 8. 



SURIRELLA AMPHIOXYS WM. SM. 



Valve oblong-linear, with cuneate ends; pseudoraphe narrow; costae, 3-4 in 10 

 strise, 14-16 in 10 n, somewhat radiate. L. 34-54 /*. 

 Surirella moelleriana Grun. 



Fresh and brackish water. Common along the coast. 

 PL 35, Figs. 12 and 13. 



SURIRELLA ROBUSTA EHR. 



Valve linear-ovate; pseudoraphe wide; alse prominent; costse wide, 1J4 in 10 

 Frustule in zone view clavate. L. 200-365 M- 

 Fresh water. 

 PI. 36, Fig. 2. 



