90 p. T. CLEVE, SYNOPSIS OF THE NAVICULOIl) DIATOMS. - 



42. D. (lidynia Ehb. (1840). — V. slightly constricted in the middle, with tongue-shaped 

 segments. L. 0,o.') to (),09; B. 0,oi7 to 0,0.36 mm. Central nodule moderately large, its horns not 

 divergent. Furrows narrow, linear. Transverse costte 8 to 10 in 0,oi mm., crossed by numerous, 

 sliglitly undulating, longitudinal costa'. — Fiminlaria didymn EilB. Kreideth. p. 75. Nav. didi/nia 

 W. Sm. B. D. XVII f. ir)4 a. A. S. Zeitschr. f. ges. Naturw. 1873 p. 405 PI. VI f. 1. A. S. 

 N. S. D. PL I f. 7. Atl. XIII f. 1, 2, 3. V. H. Syn. p. 1)0 PI. IX f. 5, (!. Suppl. B. f. 20. 

 .V. Bombns Donk. PI. VII f. 7 b, 8 b. 



Brackish and marine: Greenland! Spitsbergen! Kara! Finmark! Baltic (from Westerbotten 

 to Riigen), Caspian Sea (Grun.), Black Sea! ('eylon! Tahiti! Japan! ('ape Horn (Petit), "West Indies' 



D. didymn is a variable species, related to the var. elrsdiana of D. splrvdida and to 

 certain forms of D. Bomhus. Tlie outline of the valve becomes less panduriform and almost ellip- 

 tical as the water becomes less salt. The varieties in the northern part of the Bay of Bothnia 

 where the water is almost fresh are almost elliptical and closely connected with D. doDildlffcnsis. 



43. D. Boinlms Ehb. (1844). — V. deeply constricted, with suborbicular or elliptical seg- 

 ments often of inequal size. L. 0,06.'') to 0,i.3; B. 0,022 to 0,o4.'j; at the constr. 0,012 to 0,02.5 mm. 

 Central nodule large; its horns divergent in the middle, approximate at the ends. Farrows narrow, 

 linear. Tran.sverse costte 5 to 8 in 0,oi mm. crossed by 2 to 5 curved, longitudinal costte. Central 

 alveoli distant from the margin. — Dipl. Bomhus Ehb. Berl. 1844 p. 84 (accord, to Chase). M. G. 

 PI. XIX f 31. Nor. Bomhm Greg. D. of Clyde p. 484 PI. IX f. 12. Donk. B. D. p. 50 PI. VII 

 f. 7 a. V. H. Syn. p. 90 Suppl. B f 22, A. S. Atl. LXIX f. 28, 29. Nav. (/rmwa A. S. Zeitschr. 

 f. ges. Naturw. 1873 p. 405 PI. VI f. 2. N. S. D. PL I f. 1, II f. 1. Atl. XIII f. 4, 5, (5, 7, 8, 9. 

 Nav. ahnormis Castr. Chall. Exp. XXVIII f. 19. 



Marine: Finmark! North Sea! Marocco! Mediterranean Sea! Adriatic! Black Sea! Caspian 

 Sea (Grun.)! Madagascar! Java! Japan! Samoa! Galapagos Islands! ('ape Horn (Petit), Brazil (Atl.), 

 Florida! Campeachy Bay! Fossil: Aegina (Ehb., Atl.). 



A^ar. egcna A. S. (1875). — L. 0,o.38 to 0,04:; B. 0,oi.') to 0,02; at the constr. 0,oo6 to 

 0,012 inm. Transverse costte 8 to 9 in 0,oi mm. crossed on each side of the median line by about 

 3 longitudinal costge. — Nav. gemina v. egena A. S. Atl. XIII f. 10. 



Marine: Balearic Islands! Madagascar! Manilla! China! Japan! 



Var. densestriata A. S. (1875). — L. 0,04.^ to 0,0.5 g; B. 0,oi8 to 0,020; at the constr. 0,011 

 to 0,0 1,'-) mm. Costee 8 to 9 in 0,01 mm. — Nar. (/nni)ia r. dcnsestr. A. S. Atl. XIII f. 11, 12. 

 Nav. didyma A. S. Atl. LXIX f. 30. 



Marine: Marocco! Seychelles (Van Heurck Coll.)! California (Atl.). 



Var. bidlafa Cl. — L. 0,1.5; B. 0,047 in 0,oi mm. Horns with a row of large puncta. Costse 

 5 to 7 in 0,01 mm. 



Marine: Adriatic! Red Sea (Deby Coll.)! California! 



44. D. Kiitzingii Grun. (1860). — V. strongly constricted, with deltoid-elliptical segments. 

 L. 0,063 to 0,15; B. 0,03 to 0,085; at the constr. 0,oi4 to 0,035 mm. Horns of the central nodule 

 parallel. Transverse costtB 6 to 8 in O.oi mm., crossed by numerous (8 to 10) longitudinal, almost 

 straight or slightly undulating costpe. — Nav. Kutzingii Grun. Verb. 1860 p. 532 PL III f. 15. 

 A. S. Atl. XIII f. 22, 23, 24. Pant. I PL XXIX f. 299. 



Marine: Balearic Islands! Gulf of Naples! Black Sea! Red Sea (Deby Coll.)! Cape of 

 Good Hope! Bermuda (Rae Coll.)! Valparaiso (Atl.), Galapagos Islands! Fossil: Hungary (Pant.), 

 Aegina (Atl.). 



Var. hullata Cl. — Horns with a row of lai'ge puncta. 



Marine: Gulf of Naples! Red Sea (Deby Coll.)! 



J). KiltBinyii is very nearly akin to D. Bomhus var. drnscstriata, but it is larger and the 

 hcn'us of the central nodule are parallel. 



