4 p. T. CLEVE, SYNOPSIS OF THE NAVICULOID DIATOMS. 



5. N. microcephala G-run. (1880). — V. lanceolate, obtuse. L. 0,oi4; B. 0,oo3 mm. Areas 

 indistinct. Strife nearly parallel, about 30 in 0,oi mm. — V. H. Syn. PI. XIV f. 29. Achnan- 

 thidium microc. W. Sm. B. D. II p. 31 Suppl. PL LXI f. 380 (1856)? 



Fresh water. 



6. N. Atoraus Naegbli (1849). — V. elliptical, with rounded ends, slightly silioious. 

 L. 0,004 to 0,008; B. O.ooas to 0,oo4 mm. Areas indistinct. Striae about 30 in 0,oi mm. strongly 

 radiate throughout. — Synedra At. Naegbli in Kiitz Sp. Alg. p. 40 (according to Grunow). N. At. 

 Grun. Verb. 1860 p. 552 PL IV f. 6. V. H. Syn. p. 107 PL XIV f. 24, 25. 



Fresh water (Moist earth etc.): Belgium (V. H.). 



7. N. (Diadesmis) lucidula Grun. (1880), — V. elliptical, with broad, rounded ends. 

 L. 0,015 to 0,019; B. 0,oo8,'j to 0,oi mm. Areas indistinct. Striae 17 in 0,oi mm. slightly radiate 

 throughout, distinctly punctate, puncta forming longitudinal rows, about 17 in 0,oi mm. — V. H. 

 Syn. PI. XIV f. 40. 



Fresh water. 



8. N. minuscula Grun. (1880). — V. elliptic-lanceolate, with obtuse ends. L. 0,012; B. 0,oo5 

 mm. Areas indistinct. Strise about 30 in 0,oi mm. almost parallel. — V. H. Syn. PI. XIV f. 3. 



Fresh water. 



9. N. Ibahuslensis Gkun. (1880). — V. broadly lanceolate, with subrostrate ends. L. 0,oi3 

 to 0,02; B. 0,006 mm. Areas indistinct. Strise 25 in 0,oi mm. almost parallel. — N. minusc. v. 

 hah. V. H. Syn. PL XIV f. 2. 



Marine: West coast of Sweden! 



Var. istriana Grun. (1880). — V. more lanceolate. Strise 22 in 0,oi mm. — V. H. Syn. 

 PL XIV f. 4. 



Marine: Adriatic (Grun.). 



Var. arctica Grun. (1884). — V. broadly lanceolate. L. 0,02 to 0,021; B. 0,0095 mm. Strise 

 21 in 0,01 mm. radiate throughout. — Fr. Jos. Land, D. p. 104 (52) PL I f. 43. 



Marine: Franz Josefs Land (Grun.). 



Naviculse Decussatse Grun. (i860 p. p.). 



Valve elongated, elliptical, or lanceolate, symmetrical, not sigmoid. Structure: puncta ar- 

 ranged in obliquely decussating rows. 



This small group comprises three isolated forms, which seem not to be allied to each other. 

 N. Placentula is a fresh-water species, perhaps akin to the Pundatce, although it has no nearly allied 

 species in that group. N. decussata is too imperfectly described to decide what are its affinities. 

 The termination of the median line at a distance from the ends suggests an affinity to the section 

 MicrostigmaticcB (division Liiellus). N. Quincunx is an entirely isolated form, the structure of 

 which recalls that of some Mastogloise, but from the straight median line it may be inferred that 

 it really is a Navicula. 



1. N. Placenta Ehb. (1854). — V. elliptical, with rostrate-capitate ends. L. 0,037 to 0,039; 

 B. 0,015 to 0,017 mm. Axial area indistinct. Central area small, orbicular. Transverse striae 22 

 (middle) to 27 (ends) in 0,oi mm. slightly radiate. Oblique strise curved, crossing each other at 

 an angle of about 80°. — M. G. XXXIII, 12 f. 23. Lewis Proc. acad. nat. sci. Philad. p. 7 

 PL n f . 7 (1865). Grun. A. D. p. 47 PL III f. 60. N. apiculata Greg. M. J. IV p. 4 PL If. 13 

 (1856). N. Rostellum W. Sm. B. D. II p. 93 (1856). Grun. Verb. 1860 p. 550 PL IV f. 10. 

 DoNK. B. D. p. 40 PL VI f. 7. 



