ACTINOCYCLUS. 523 



A good monograph of this genus was published in 1890 by Rattray, under 

 the title of " A revision of the genus Actinocyclus" to which we refer the reader 

 who desires to study exotic species of this genus. 



Figure 1:78 in the text represents A. Ralfsii, the type-form of our regions. 



A. Ralfsii (W. Sm.) Ralfs. (in Pritch., p. 835 ; Eupodiscus 

 Ralfsii IV. St,,., S.B.D., ii., p. 86; H.V.H. Atl., pi. 123, f. 6*; in Type No. 

 518 and var. in Type No. 516 and var. in Type No. 517), plate 23, fig. 658. 



Valve circular, with large submarginal pseudo-nodule. Puncta interrupted 

 by very numerous subulate hyaline spaces, arranged in several rows and giving, 

 at a low magnification, the appeaiance of concentric zones; 5 rows of puncta 

 at the middle of the ray at the superior extremity of the innermost zone in 

 1 c.d.m. Margin furnished with small spines, almost marginal, distant about 

 1 c.d.m. from one another; puncta very fine, in quincunx, about 14 rows 

 in 1 c.d.m. Diameter of valve, 10 to 13 c.d.m. 



Marine. Very rare : Blankenberghe, Ostend, Antwerp (Scheldt, H.V.H.), France (Breb!), 

 England (W. Sm. ! Kitton, Stolt., Comber), Scotland (Cole ! Baxter Coll., No. 2689), Cuxhaven 

 (Bessel), Marstrand (Sweden, Thum. !), Ireland (O'Meara). 



var. sparsus (Greg.) Ralfs. Rows radiating, excessively distant 

 at the central portion of the valve (about 8 in 1 c.d.m.) then augmenting 

 regularly and progressively so as to form conspicuous concentric zones. 



The opinions of authors differ greatly on this form, while Gregory, 

 Ralfs, Kitton, and others see in it only a variety of A. Ralfsii. Mr. 

 Rattiay, on the other hand, thinks right to make it a distinct species, at 

 least provisionally. 



Marine. Scotland : Glenshira Sand (Weissflog ! Gregory). 



A. Ehrenbergii Ralfs. (in Pritch. Inf., p. 8 34 ; H.V.H. Atl., 

 pl. 123, f. 7 ; Type No. 518), plate 23, fig. 659. 



Valve circular ; pseudo-nodule very large, submarginal ; connecting zone 

 slightly or not marked ; hyaline spaces very narrow and few ; puncta 

 approximate, 8 radiating rows in 1 c.d.m. Margin with small spines about 

 1 c.d.m. from one another ; puncta in quincunx, about 16 rows in 1 c.d.m. 

 Diameter of valve, 6 in n c.d.m. 



Marine. Blackenberghe, Scheldt at Antwerp (H.V.H.), Cherbourg (Breb.), England, 

 various localities, Cuxhaven (Mbller, etc.). Found on all our coasts. 



A. crassus H. Van Heurck. (H.v.H. Atl, pi. 124, f. 6 and 8*), 

 plate 23, fig. 660. 



Valve orbicular, with pseudo-nodule submarginal, and furnished with 

 very small submarginal spines, indistinct in small specimens. Puncta strong 



