24 p. T. CLEVE, SYNOPSIS OF .THE NAVICULOID DIATOMS, " 



forms of Nav. Gastrum closely resemble smaller forms of Nav. j^cref/rina car. Menisctilus, from 

 which they differ by the terminal striae -being radiate throughout, but this characteristic is some- 

 times excedingly delicate. 



32. N. leptostigma Ehb. (1854). — V. elliptical, with more or less broad, rostrate ends. 

 L. 0,038 to 0,048; B. Co is to 0,o2 mm. Axial area indistinct. Central area large, orbicular. 

 Strise 14 in 0,oi mm., radiate throughout, distinctly punctate (puncta about 22 in O.oi mm.) in 

 the middle alternately larger and shorter. — Pinnul. leptost, Ehb. M. Gr. XXXIII: 1 2 f. 25. Nav. 

 lept. Icon. n. PI. I f. 37. 



Fresh water: Oregon, fossil! 



33. N. platj'stoma Ehb. (1838). - V. elliptic-lanceolate, with broad, rostrate ends. L. 0,037 

 to 0,05; B. 0,0 17 mm. Axial area narrow. Central area large, transversely dilated, subrhomboidal. 

 Strife 17 in 0,oi mm., very finely lineate, radiate throughout. Among the median striae a few 

 shorter frequently occur. — Ehb. Inf 178 PI. XIII f. 8. M. G. XIII f. 6 b. Cl. A. D. p. 14 

 PI. Ill f. 61. N. macromphala Schum. Preuss. D. II N. p. 55 PL II f 29 (1867)? 



Fresh and slightly brackish water: Sweden (Lake Malaren, Gulf of Bothnia, Gotland in the 

 Baltic)! Mouth of Jenissey! Michigan! 



Var. hcngalensis Grun. Ms. — V. subrhomboidal, with broad, rounded ends. L. 0,03; B. 0,oi2 

 mm. Strife distinctly punctate. 



Fresh water: Bengal (Grun.). 



34. N. ovifonuis Cl. N. Sp. — V. elliptic-lanceolate. L. 0,045; B. 0,oi8 mm. Axial area 

 narrow, linear; central area large, orbicular. Striae 10 in 0,oi mm., radiate throughout, finely 

 lineate, not alternating in length in the middle. — PI. II f. 4. 



Marine: Madagascar (Van Heurck Coll.)! 



35. N. arata Grun. (1882). — V. lanceolate, gradually tapering from the middle to the 

 obtuse ends. L. 0,06 to 0,o67; B. 0,oi8 to 0,02 mm. Axial area narrow; central area orbicular. 

 Strife 8 to 9 in 0,oi mm. closer towards the ends, all radiate and distinctly punctate. Across the 

 striee on each side of the median line are 3 to 4 narrow longitudinal clear areas. — N. Tuscula 

 V. arata Grun. F. D. Ost. Ung. p. 145 PI. XXX f 58. Pant. Ill PI. XXIII f. 342. 



Brackish or fi-esh water: Hungary, Dubravica fossil (Grun.), Hudson River ((Drrun.). 

 This species can scarcely be a variety of JSf. tuscula, the terminal strife being radiate. It 

 seems rather to belong to the group of N. Gastrum. 



36. N. Clemeiitis Grun. (1882). — V. slightly asymmetrical, broadly lanceolate, with rostrate, 

 obtuse ends. L. 0,o4 to 0,045; B. 0,oi2 to 0,oi5 mm. Axial area narrow. Central area small, 

 orbicular, with 2 isolated puncta on one side of the central nodule. Strife 8 to 10 in 0,oi mm. in 

 the middle, where they are alternately longer and shorter, 16 in 0,oi mm. towards the ends. All 

 strife are strongly radiate and finely punctate. — F. D, Ost. Ung. p. 144 PI. XXX f. 52. 



Fresh water: Dubravica, Hungary, fossil! Cheshire, England (V. H. T.). 

 This species is akin to iV^. Placentula and at the same time to N. Demerarre of the section 

 Punctatae, the latter having also isolated puncta on the central area. 



37. N. areiiariaet'ormis Pant. (1889). — V. lanceolate, obtuse. L. 0,02; B. 0,oi 1 mm. Axial 

 area distinct; central area small. Strife 12,5 in O.oi mm., strongly radiate to the ends, the median 

 strise alternately longer and shorter. — Pant. II p. 42 PI. VlII f. 140. 



Brackish water: Hungary, fcssil (Pant.). 



38. N. ludloviana A. S. (1876). — V. lanceolate, with obtuse, subtruncate ends. L. 0,09; 

 B. 0,03 mm. Axial area distinct, dilated around the central nodule. Strife 8 (middle) to 9 (ends) 



