156 NATURAL HISTORY SOCIETY OF DUBLIN. 



This form is exceedingly rare ; only one specimen has as yet come 

 under my notice — and this an imperfect one — but still sufficient to in- 

 dicate the characteristics ; it is, therefore, not without some misgiv- 

 ings I venture to notice it, although the marked peculiarities of it, as I 

 consider, justify me in doing so. 



In respect of the fasciculate arrangement of the areolae, there is a 

 great similarity between this species and Cos. symmetricus, and Cos. 

 Normanni. The areolae, however, are smaller than in the former, and 

 larger than in the latter. 



Ewpodiscus eccentricus. — Fig. 2, x 800, N. sp., O'M. Diameter 

 about 0014 ; surface of the valves distinctly areolate ; the areolae, which 

 are larger towards the centre than towards the circumference, are ar- 

 ranged eccentrically ; there is a marginal blank space, in which the 

 processes, about twenty in number, are placed at equal distances. 



Stauroneis rhombica. — Pig. 3, x 600, ~R. sp., O'M. Length of 

 valve, -0017; greatest breadth, -0012; rhomboido-elliptical, with 

 narrow lanceolate apices; striae very fine, punctate, and parallel; 

 stauros narrow ; the transverse limb of uniform breadth, and equal in 

 length to half the breadth of the valve. 



Stauroneis costata. — Fig. 4, x 600, K sp., O'M. Length of valve, 

 •0021 ; breadth, *0009 ; narrow- elliptical, rounded at the ends; striae 

 distinctly costate, and gently waved; the transverse limb of the 

 stauros short, and of equal breadth throughout. 



Cocconeis clavigera. — Fig. 5, x 600, N. sp., O'M. Valve broadly 

 elliptical; length, -0014; breadth, *0011; striae costate; the costae ra- 

 diate, club-shaped, and very fine at the median line, and gradually ex- 

 panding towards the margin ; not reaching the margin. 



Cocconeis Wrightii. — Fig. 6, x 800, S". sp., O'M. Valve broadly 

 elliptical; length, -0017; breadth, -0012; a narrow border is closely 

 studded with slightly elongated cellules ; the central nodule is ex- 

 panded in the form of two crescents, touching at their convex centre, 

 and radiating towards the apices ; striae moniliform, arranged in curves, 

 nearly parallel with the limbs of the crescent-like expansions of the 

 central nodule. 



Cocconeis Portei—'Fig. 7. x 800; N. sp., O'M. Valve very mi- 

 nute; length, -0009; breadth, *000 7 ; broadly elliptical, with a narrow 

 border ; striae radiate, punctate ; the puncta very minute at the median 

 line, and gradually enlarging towards the outer margin ; the median 

 line broad. 



Rhaphoneis liburnica, var. — Fig. 8, x 600. Valve broadly ellip- 

 tical; length, *0018 ; breadth, *0014; striae radiate; the cellules, 

 which are not more than six in the longest stria, appear slightly pro- 

 jected above the surface of the valve, are quadrangular at the base, 

 narrower and rounded towards the top ; rhaphe narrow, elliptical ; valve 

 without border, margin striated. At first I was disposed to regard this 

 form as a distinct species, but, on consideration, preferred to refer it to 

 Rhaphoneis liburnica, Grunow. 



The specific description of R. liburnica given by that author agrees 



