54 P. T. CLEVE, SYNOPSIS OF THE NAVICULOIIJ D1AT(KMS. 



each side of tlie median line. Stritu sligbtly radiate in tlie middle, elsewhere paralld. 19 in Cm 

 mm. — Nav. Kain. Pant. III Pl. III f. 41. 

 Habitat?: »Köi^ecz. (Pant.). 



17. C. obtusa W. Sm. (1853). — V. very convex, .subrectangi;lar, with broad, truncate ends. 

 L. 0,05 to 0,06; B. 0,0 it; to 0,oi7 mm. Axial and central areas nnited in a moderateh' broad 

 lanceolate space, in tlie middle of whicb is on each side of tbe central nodule a lunate marking 

 Striffi 17 in 0,oi mm. parallel or slightly divergent towards the ends. Longitudinal lines sub- 

 marginal. — Nai\ obtusa W. Sm. B. D. I p. 50 Pl. XVI f. 140 (1853). Grun. Verli. 1860 p. 53fj 

 Pl. IV f. 39? K Hebes Ralfs Priteh. Inf. p. 896 (1861). Donk. B. D. p. 23 Pl. III f. 12. 



Fresli water, especiallj' in notbern regions. Greenland! Sweden, Lappland and Gotland! 

 Hussian Lappland! Norway, Dovre! Scotland! 



This species is verj^ cbaracteristic and not closely akin to any known form. It seems to 

 be an inbabitant of northern regions and is not mentioned by Brun as occuring in Switzerland, 

 nor by Belloc as occuring in the Pyrenées. 



18. C. Liber W. Sm. (1853). — V. linear, sometimes with slightly concave or convex 

 margins, and rounded or subcnneate ends. L. 0,o.5 to 0,i9; B. 0,oo8 to O, os 2 mm. Axial area in- 

 distinct or very narrow. Central area indistinot or small. StricP 13 to 20 in 0, 01 mm. parallel. 

 divergent at the ends. Longitudinal lines median, single or double. 



A. Forms with linear, sometimes slightly constricted valves, and without lunate markings 

 in the central area. 



a) Longitudinal lines single. 



Var. linearis Grun. (1860). — V. narrow, linear, with parallel margins and rounded ends. 

 L. 0,054 to 0, 12; B. 0,008 to 0,011 mm. Areas indistinot. Strise 20 to 29 in 0, 01 mm. Longitu- 

 dinal lines median, frequently indistinct. — Nav. linearis Grun. Verb. 1860 p. 546 Pl. III f. 2. 

 V. H. Syn. p. 105 Pl. XII f. 35. A. S. Atl. L. f. 38, 40. 



Marine: Atlantic coasts of Europé, Africa and America (Grun.), Ceylon! Singapore (Brun 

 Coll.!) Galapagos Islands! Peru (Grun.), Honduras (Grun.), Gulf of Mexico (Atl.). 



Var. genuina Cl. — V. linear, with parallel or slightly con-s-ex margins and more or less 

 broad ends. L. O, os to 0,17; B. 0,oi3 to 0, 024 mm. Axial area very narrow; central area small, 

 orbicular, frequently somewhat asymmetrical. StritE 13 to 20 in 0,oi mm. — Nav. Liber AV. Sm. 

 B. D. I p. 48 Pl. XVI f. 133. Donk. B. D. p. 62 Pl. IX f. 5. A. S. Atl. L. f. 16, 17, 18. A. S. 

 N. S. D. n f. 45. V. H. Syn. p. 104 Pl. XII f. 36. Nar. maxima Greg. M. J. IV Pl. V f . 2 

 (1856). D. of Cl. p. 487 Pl. IX f. 18. A. S. Atl. L. f. 19 to 21, 37. N. S. D. II f. 44. Nav. 

 fortunata Leud. Fortm. D. de Ceylan Pl. III f. 27 (1879). 



Marine: Greenland! Spitsbergen! Finmark! Behrings' Island! Xorth Sea! Mediterranean 

 Sea! Red Sea! Seychelles! Cape of Good Hope! Ceylon! Singapore! Sidney! Port Jackson! Tas- 

 mania! Philippines! Japan! Campeachy Bay! 



Forma tenaistriata Cl. — L. 0,o65 to 0,07; B. 0,oi5 mm. StriiB 25 to 26 in 0,oi. 



Marine: Labuan! Sandwichs Islands! 



Forma convexa Cl. — Convex. L. 0, 11 to O.ia; B. 0,012 mm. Axial area somewhat broader. 

 Strise 16 to 20 in 0,oi mm. — Nav. Haueini Cl. N. E. D. p. 9 Pl. II f. 27 (1881). 



Marine: Gulf of Naples! Adriatic! 



Var. Holnboi Pant. (1886). — V. linear, with rostrate capitate ends. L. 0.i5'.i; B. 0.o2.t mm. 

 Strise 20 in 0, 01 ram. — Nav. {maxima var.?) Hal. Pant. I p. 25 Pl. XVIII f. 165. 



Marine: Hungary, fossil (Pant.). 



Var. relegatu Cl. — V. slightly constricted in the middle, with cuneate ends. L. O.15; B- 

 0,025 mm. Axial area linear-lanceolate. StricB 12 to 13 in 0,oi mm., crossed by a median longi- 

 tudinal Une. 



Marine: Redondo, Calif fossil (Grove Coll.)! 



