406 DESCRIPTION OF [Pol^gastrtca. 



SuEiErxLA Sicnh = Navicula Sicnla. — Smooth, and broadly navi- 

 cular laterally ; the margin with longitudinal lines ; ends subacute- 

 Length l-528th. 



^v-RiuEhTakAmphiboia. — Striated, and mdely linear; on the lateral 

 surface cuneate, subacute at the extremities ; on the dorsal aspect, 

 ends obtuse ; pinnules fifteen in 1-1 200th. Length 1 -324th. Has 

 the general form of S. Regula. Kurdistan. 



Ehrenbcrg remarks, that he is not sure to what genus this belongs ; 

 he has sometimes thought a slender umbilicus existed, as in Pinnu- 

 laria ; but its fonn is singular, in presenting equal transverse striae 

 on each side. 



S. Irevis. — Short, striated ; has the figm^e and size of S. striatula, 

 but its strise are larger and more slender; sixteen in l-1200th. 

 Length 1-9 12th. Kurdistan. 



S. Lepida. — Slender,linear lanceolate, one end extremely obtuse, the 

 other more tapering and subacute ; striae nine to ten in 1-1 152nd ; a 

 distinct curved line extends along the centre on each lateral aspect. 

 Length 1-76 8th. Kurdistan. 



S. (?) elli2}tica. — Elliptic-oblong; a slight longitudinal line extends 

 down its centre, and it has parallel transverse striae. Length 

 1 -480th. In form approaches the genus Rliaphonek. 



S. cremdata. — Ovate lanceolate, margin crcnulate ; ends somewhat 

 unequal, subacute ; eleven crenules in 1-1 152nd, extending into pin- 

 nules. It has also a distinct median suture. Diam. l-1080th. Fossil. 



S. IcBvigata. — Lmceolate, elongate, smooth, ends obtuse, somewhat 

 unequal ; a distinct median suture exists, with two longitudinal 

 lateral lines. Length l-168th. 



S. leptoptera. — Lanceolate, ends acute, rather unequal ; pinnules 

 dense, six in 1-1 152nd; median suture dilated, distinct. A specimen, 

 1 -456th long, presented twenty-one pinnules. Fossil, Oregon. 



S. Oregonica. — Spathulate in figure, ends subacute, unequal ; 

 median suture broad and distinct ; pinnules strong ; about the middle, 

 from four to five in 1-1 152nd, Length l-336th, and in this nineteen 

 pinnules were met with. Fossil. 



S. reflexa. — Lanceolate, extremities unequal, subacute, slightly 

 reflexed ; central suture distinct ; pinnules strong, about centre three 

 to four in 1-1 152nd. Length 1-1 80th. Fossil in Oregon, 



