9 



Cyclas cornea (Tbe Horny Cycle). Linnem^ 

 Figures 3 and 4. 



Cyclas cornea is not nearly so large as C, riyicola. 

 It varies considerably in its form, though mostly very 

 round. It also varies in colour, but is usually of a 

 brownish hue. The umbones are, in nearly all the 

 specimens, broad. It is one of our most abundant 

 species. The length of the shell is nine-sixteenths by 

 seven-sixteenths broad. The usual size in this neigh- 

 bourhood is five-twelfths of an inch long, half an inch 

 broad, and four-twelfths of an inch in ventricosity; but 

 iu this latter respect there is much variation. 



The diversity in form and size of the Horny Cycle 

 has occasioned conchologists to recognize several seem- 

 ingly distinct varieties, yet, most probably, it is locality 

 only, which causes the variation. Mr. Gough bas sent 

 me two varieties, found near Kendall ; the first in the 

 mud of a small mountain tarn, which is very diminutive, 

 almost white, and very slightly ventricose; the second 

 from ditches on peat bog, near Morcamb Bay, it varies 

 but little, except in size, from the common form of 

 Cyclas cornea. A much more distinct variety was sent 

 to rue from Darlington, in Durham, by Mr. Graham ^ 



