KONGL. ,SV. VET. AKADEMIENS IIANULINGAH. BAND 26. N:0 2. 45 



4(i. r. foriuosiiiii W. Sm. (liibi). — V. iiarrow, linear-lanceolate, gently signioid, gradually 

 aml imilaterally narrowed towai'ds tlie eiids. L. 0,i4 to 0,!>3; B. 0, 02 to 0,o.5 mm. Median line 

 sigmoid, exceiitric, generally for a coiisiderable distauce coiiicident with the convex margin. Olilique 

 strise crossing each otlier at an angle of 90°. Transv. and obl. stritc "/i,„ '^Z,,, -%e in 0, 01 mm. — 

 W. Sm. Ann. M. Nat. H. [2] IX p. 5 Pl. I f. 1. B. D. p. 63 Pl. XX f. 195. Grun. A. D. p. 48. 

 V. H. Sjoi. p. 116 Pl. XIX f. 4. Per. I f 3 to 5. P. australicum O. Witt. Mus. Godeff, p. 70 

 Pl. VIII f. 7 (1873). P. (Iccorum. W. Sm. I p. 63 Pl. XXI f. 196. Grun. A. D. p. 49. V. H. Syn. 

 p. 116 Pl. XIX f. 1. Per. I f. 11 to 13. P. htJdtense O. Witt. Mus. Godeffr. p. (57 Pl. VIII 

 f. 13 (1873). 



Marina: North Seal Mediterranean Sea! Red Sea! Java! China! Behrings Island! Sandwichs 

 Islands! Galapagos Islands! "West Indies! 



Var. dahnaiica Grun. (1880). — V. narrow, slender, acute, slightly sigmoid. L. 0,25 to O, .32; 

 B. 0,03 mm. Median line slightly excentric. Transv. and obl. strite '^/|2, 'Vu i'^ '^i'" "^™- — 

 P. decor. var. dalm. Grun. A. D. p. 49. Per. II f. 6 to O?. Icon. n. Pl. IV f. 21. 



Marine: Balearic Islands! Adriatic (Grun.)! 



Var. {Ehoicosignia) Arens Cl. — V. arcuate. L. 0,2; B. 0,02 mm. Transv. and obl. strisB '7i3 

 in 0,01 mm. — Pl. IV f. 18. 



Marine: Macassar Straits (Grove Coll.)! 



Var. halearica Per. (1891). — V. linear, with unilaterally rounded ends. L. 0,3.i to O, .^4; B. 

 0,034 to 0,06 mm. Transv. and obl. striaj i-^/g, 'V91 '% in 0,oi mm. — Per. p. 4 Pl. I f 6, 7. 



Marine: Mediterranean Sea (Per.), Singapore ((xrove Coll.)! 



Var. longissima Grun. (1880). — V. lanceolate, sigmoid. L. 0,4 to 0,78; B. 0,085 to0,n73mm. 

 Median line sigmoid, excentric at the ends. Transv. and obl. strise 'Vio- 'Vm ''''/12' 'Vis; "lu "i 

 0,01 mm. — Grun. A. D. p. 48. Per. p. 4 Pl. I f. 1, 2. 



Marine: Puerto Caballo (Per.), Colon! Campeachy Bay! Samoa! China! Java! Galapagos 

 Islands! 



All the forms from P. njjeciosam are very nearly connected and might be uiiited into one 

 single species, characterized by the oblique stria- crossing each other at an angle of about 90°. 

 Between P. formosuiu and P. decormn there is absolutely no specific diiference, and by numerous 

 varieties P. formosum graduates into P. pulch,rwm and P. speciosum. By the var. dcdmaticn P- 

 formosum is connected with P suhriqiduw, P. hiif/iiDi, and P. Pfvat/alli, which latter is intermediate 

 in the passage to P. NuhccuJa. -— Donkima reticulafa Norm. (Grev. in T. Bot. Soc. Ed. vol. VIII 

 p. 237 Pl. III f. 13, 14. Pritch. Inf. 1861 p. 921) is probably akin to the last described species. 

 It is a large form (L. O, le mm.) with very excentric median line and highly carinated valves. 

 Oblique strife about 8 in 0, 01 mm. This form, found in Western Australia, is entirely unknown 

 to me. A somewhat similar form occurs in Oamaru dejjosit but I have seen only some incomplete 

 specimens. L. 0,2. Strise 10 in 0, 01 mm. 



Toxonidea Doxkin (1858). 



Valve asymmetrical, thin. Median line arcuate, excentric. Axial area indistinct. C^entral 

 area indistinct. Structure the same as in Pleurosigma. Zone not complex. 



This genus cumprises asymmetrical forms of Pleurosigma. The cell-contents are not knowu, 

 but will probably offer some interesting peculiarities. 



1. T. insignis Donk. (1858). — V. strongly asymmetrical, with almost straight dorsal and 

 very convex ventral margin. Ends subrostrate. L. 0,i2 to 0,13; B. 0,025 to 0,03 mm. Median 

 line strongly excentric, eoincident at the ends for some distance with the dorsal margin. Transv. 



