i j. Vrea with about 40 sub-parallel rows of puncta on eai h side 

 of a more or less apparent blank Raphe. 



( \ imperialis, Grev. 



14. — Area without sub*parallel punctate striae, and without appear- 

 ance of a Raphe (15). 



15. — Area with three or four squares one within the other, formed 

 by conspicuous dots surrounded by scattered finer 

 puncta. C. miradi/is, Leud. 



16. — Area without quadrate rows of dots (17). 



17. — Radials and inter-Radials rough with minute apiculi (19). 



18. — No apiculi (21). 



— Rays from 40 to 60 in number. C. Hibernicus^ Ehr. 



— Rays from 90 to roo in number. C. noricus* Ehr. 



19 



20 

 21 



Inter-Radials with 2 or 3 rows of puncta : margin of valve 

 double; circlet of large beads. C. ornatus^ Grev. 



22. — No inter-Radial rows of puncta, no double border (23). 



23. — Area angular at top and bottom (25). 



24.— Area rounded at extremities (27). 



25. Area coarsely granular. Rays smooth. Indication of a 



central smooth line. C. eximius, Greg. 



26. — Area finely punctured, clepsydrate. Rays with a row of 



dots. No indication of a central line. 



C. Pantocsekii) Deby. 



27. — A circlet, formed by a row of short lines or of dots (35). 

 28. — No distinct circlet formed by one row of lines or beads (29). 



* Through the great kindness of the Count Barbo, of Milan, I have had 

 an opportunity of examining the C. /.anus of Castracane, which I now possess, 

 both from the Lake of Como and the Lake of Varese, and which I consider 

 a finedined variety only of C. noricus, Ehr. 



