KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 26. N:0 2. 47 



first, the presence of longitudinal lines and secondly, the strire, -whicli are not distinctly pimctate, 

 the strifE of all the species of Pleurosigma being punctate. 



An asymmetrical tendency is slightly apparent in several forms of C. LiJier, and is very decided 

 in C. {Alloioneis) curvinerins. Among the Amphora' are many forms with longitndinal lines, bnt 

 no known species of that genns is closely connected with Coloneis. — There are varions transitions 

 among the forms of Caloneis. Some species are slightly eonstricted in the middle or biconstricted, 

 and thns connect the non-constricted forms with tlie pandnriform or strongly biconstricted. 



Closely connected with Caloneis is the genns Fseudociinphiprora, among the species of whicli 

 P. iiiipleta comes nearest. The principal distinction betvveen these two genera consists in the na- 

 ture of the strite, -which are pnnctate in Fseudoa »iplciprora . The transverse expansion of the cen- 

 tral nodule of Psendo-amphiprora is met with in some species of C!aloneis, as for instance C. Wardii. 

 — The terminal fissures in most forms of the type C. Liher are not very divergent from the 

 direction of the median line, and being sitnated on the concave end of the valve, they liave the 

 appearance of short flexnose lines (see A. Schmidfs Atl. Pl. L.). In C. ahnormis they are-turned 

 in contrary directions. In the forms of the type C. Poivellii and in tlie pandnriform species they 

 are small and indistinct. 



The striiT' are as a rnle transverse, in some forms slightly radiate, and are nsnally di^'ergent 

 at the ends, not convergent as in Pinnularige,. They are generally smooth or not distinctly punctate, 

 excepting in the donbtfnl C. disperva, which has distinctly pnnctate stria'. — In addition to the 

 natnre of the stria3, the longitudinal lines are a very characteristic featiire of Caloneis. In many 

 species the valves are divided by these lines into an inner plane, or even concave, portion; and an 

 outer portion whicli is convex and sloping. In other species the inner portion appears to be more 

 elevated. Without transverse sections of the valves it is extremely difhcult to ascertain which 

 is the case; but as a rule the plane, or inclination, of the part of the valve which is within the 

 longitndinal lines is different from that of the outside parts. Transitions of all kind soccur, from the 

 narrow true lines of C. Liber and others to the broad bands of C. Castracanei, C. mirahilis etc, 

 shewing that, whether narrow or broad, these lines are of the same natnre. — In C. Madagascarensis 

 there are, in addition, other fainter, longitudinal lines, formed bj- knöts on the strige; and this 

 fact seems to point to an affinity between Caloneis and Tropidoneis (T. lepidoptera, T. longa). 



1 



Ärtifidal key. 



j r'entral nodule stauroid C. ^Vardii Cl. 



\ — — not — ■ 2. 



Central area a transverse fascia 3. ') 



— — not — — 19. 



„ j Valve sigmoid C. staurophora Grun. 



I — straiglit 4. 



. j Linear or almost linear 5. 



\ Lanceolate, constricted or biconstricted 11. 



Stria; radiate C. Clevei Laost. 



parallel 6. 



area rather broad 7. 



narrow or indistinct 8. 



_ J Marine species C. latefasciafa Grun. (C. formosa var. interrupta). 



\ Freshwater species C. patagovicu Cl. 



^ ) Margins parallel 9. 



\ — slightly undulate _' C. Silicula var. 



fj j Striae 15 in O.oi mm C. consimilis Å. S. 



'■ 1 — flner 10. 



. I Str. 



„ I Axial are; 

 '• i - - 



' To this division belongs C. nuMcola Grun., whicli for vant of flgure and roniplete description cannot be enrolled 

 in the kev. 



