Kavictdacea.'] iNFFSoniAt animalcules. 411 



Navicula rostrata. — Large, very broadly lanceolate, almost rliom- 

 boid ; extremities acute, rostrate. Centi'al aperture large, lateral view 

 linear, truncate. Length 1-2 16th. Fossil. 



N. affinis. — Linear dorsally, constricted at each end, which is 

 shortly rostrate and obtuse. Approaches Plmiularia dicephala. Length 

 l-570th to l-420th (P. 15, f. 32.) 



N. amhigua, — Linear-oblong dorsally, sub ven trie ose, contracted at 

 each end, which is produced but obtuse. Resembles very closely 

 the former species. 



N. (?) Americana. — Oblong and turgid dorsally, slightly constricted 

 in the middle ; ends widely rounded. 



N. (?) amfliigomphus. — Larger, oblong ; sides smooth ; ends wedge- 

 shaped, with or without faint longitudinal lines. 



N. amphioxys. — Dorsally narrow, linear lanceolate, without longi- 

 tudinal lines or striae, attenuated at the ends, subacute. More 

 elegant in figure than N. gracilis. 



N. amphirhynchus. — Dorsally elongated, lanceolate, suddenly con- 

 sti'ictcd towards the ends, which are produced and truncate (P. 15, 

 f. 6.) Has a wider foi'm than N. amphishcena. 



N. amphisphcma. — Dorsally acutely lanceolate, gradually attenu- 

 ated towards the ends ; umbilicus oblong, in which it differs from 

 N. fulva, which has a round umbilicus. 



N". Bacilhon. — Smooth, linear dorsally and bacillar ; ends rounded. 



N. biceps. — Smaller than preceding, dorsally broadly lanceolate ; 

 apices rather constricted, but obtuse. Mexico and North America. 



N. carassius. — Small, widely lanceolate on back ; ends suddenly 

 constricted, obtuse, but rather prolonged. Shorter and wider than 

 N. amphinbana. Surinam. 



N. dilatata. — Large, dorsally elliptic-lanceolate, laterally rather 

 convex, with longitudinal lines ; ends obtuse. 



N. JDirhynchis. — Small, dorsally narrowly lanceolate ; ends elon- 

 gated, rostrate, obtuse. Mexico, Labrador. 



N. dubia. — Small, linear lanceolate on back ; sides rather cui'ved, 

 the curve extending to the subacute prolonged ends. Surinam. 



IS. duplicata. — Oblong, small ; constricted at the middle (panduri- 

 form) ; ends attenuate. A^])roaches Pinnularia didyma. Cuba. 



E E 2 



