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



first, the presence of longitudinal lines and secondly, the striee, which are not distinctly punctate, 

 the striae of all the species of Pleurosigma being punctate. 



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

 in C. (Alloioneis) curvinervis. Among the Amphoree are many forms with longitudinal lines, but 

 no known species of that genus is closely connected with Colonels. — There are various transitions 

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

 and thus connect the non-constricted forms with the panduriform or strongly biconstricted. 



Closely connected with Caloneis is the genus Pseudoamphiprora, among the species of which 

 P. impleta comes nearest. The principal distinction between these two genera consists in the na- 

 ture of the strise, which are punctate in Pseudoamphiprora. The transverse expansion of the cen- 

 tral nodule of Pseudo-amphiprora is met with in some species of Caloneis, as for instance C. Wardii. 

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

 direction of the median line, and being situated on tlie concave end of the valve, they have the 

 appearance of short flexuose lines (see A. Schmidt's Atl. PL L.). In C. abnormis they are turned 

 in contrary directions. In the forms of the type C. Powellii and in the panduriform species they 

 are small and indistinct. 



The strife are as a rule transverse, in some forms slightly radiate, and are usually divergent 

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

 excepting in the doubtful C. dispersa, which has distinctly punctate stria. — In addition to the 

 nature of the striae, the longitudinal lines are a very characteristic feature of Caloneis. In many 

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

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

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

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

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

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

 shewing that, whether narrow or broad, these lines are of the same nature. — In C. Madagascar ensis 

 there are, in addition, other fainter, longitudinal lines, formed by knots on the striae; and this 

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



■r 



, ( Centr: 

 ^•1 - 



Artificial key. 



Central nodule stauroid ... C. Wardii Cl. 



— not — . . .... 2. 



Central area a transverse fascia .... ... 3. ') 



- not — — . . . .... 19. 



„ ( Valve sigmoid . . . . C. staurophora Getjn. 



\ — straight ... . .... 4. 



I Linear or almost linear 5. 



\ Lanceolate, constricted or biconstricted . . . . 11. 



p. J Strise radiate C. Clevei Lagst. 



' ' \ — parallel . . . .6. 



„ 1 Axial area rather broad .... ... 7. 



■ \ — — narrow or indistinct . . ... 8. 



( Marine species . . C. latefasciata Gbun. (C formosa var. interrupta). 



■ \ Freshwater species . . C. patagonica Cl. 

 J Margins parallel i .9. 



\ — slightly undulate .... . . . C. Silicula var. 



Stris 15 in 0,oi mm. . C. consimilis A. S. 



I Stri 



finer . . . . ... . . . 10. 



' To this division belongs C. nubicola Gedn., which for vant of figure and complete description cannot be enrolled 

 in the key. 



