Naviculacea.'] infusoeial animalcules. 481 



which, viewed laterally, are truncate, and dorsally very acute. Length 

 l-72ud. In ponds. Dalinatia. 



Stnedra curvida. — Long, slightly curved ; laterally rather tapering 

 towards the truncate end ; dorsally acuminate, with somewhat acute 

 apices. Yar. b. Testule longitudinally dotted. Length 1 -240th. 

 Fresh water. 



S. Arcus. — Laterally linear, truncate, and curved; dorsaUy straight, 

 lanceolate, with acute ends. Length 1 -420th. Gulf of Genoa. 



S. debilis. — Small, linear, margin indistinctly striated ; dorsally 

 produced into a point ; laterally rather attenuate and trunca te 

 Length 1 -620th. 



S. notata. — Small, with the margin obsoletely striated; laterally 

 oblong, truncate ; dorsally elliptic, long, with the apices almost 

 round and obtuse. Length 1 -650th. 



S. Martensiana. — Smaller, distinctly striated ; laterally linear, trun- 

 cate ; dorsally lanceolate, gradually tapering, and somewhat acute. 

 Length 1 -600th. 



S. Vaucherice. — Small, very delicately striated ; truncate laterally ; 

 dorsally attenuated near the apex and acuminate. Length 1- 780th. 



S. lanceohta. — Rather small ; dorsally lanceolate, distinctly striate ; 

 marked by a transversely median rhomboid and perfectly smooth 

 band ; laterally narrowly linear, slightly attenuate at the middle. 

 Length l-600th to l-310th. 



S. acuta. — Large; laterally, perfectly linear and truncate; dorsally, 

 suddenly acuminate near the apex. Length 1-1 44th. Trinidad, 

 Peru, Mexico, Chili. 



S. oxyrhynchus. — Large, linear; dorsally naiTowed towards the 

 apex, which is acuminate. Length l-280th to l-144th. 



S. tergestina. — A variety of S. Ulna, presenting laterally a sigmoid 

 form. Trieste. 



S. mesolepta. — DeKcate, linear ; laterally attenuated near the mid- 

 dle ; dorsally slightly bent, sometimes subsigmoid, gradually acu- 

 minate. Length 1-1 60th. 



S. equalis. — Large, linear; laterally, dilated at each extremity; 

 dorsally, with the apex rather tapering, but obtuse and rounded. 

 Length 1 -140th. 



