CYCLAS. 253 



The shell is rather solid, opaque within ; the um- 

 bones paler and often circumscribed with a dark line ; 

 length 10J, height 8J, thickness 6| lines. 



115. 2. CYCLAS cornea. Horny Cycle. Shell sub- 

 orbicular, globose, thin, very finely striated ; 

 umbones blunt ; ligament inconspicuous, (t. 

 1. f. 2.) 



Tellina cornea. Linn, S. N. i. 1120. ; Linn. Trans, viii. 59. ; 

 Don. B. S. t. 96. Sphserium corneum. Scopol. Int. H. N. 

 398.; Bourg. Spcer. 21. Cyclas scaldiana. Norm. Cycl. 

 5. t. 5. f. 12. Sphaerium scaldianum. Norm. Cycl. t. 1. 



Sphaerium citrinum. Norm. Cycl. Nux nigella. Humph. 

 Cat. 59. Tellina rivalis. Mutter, Verm. Hist. ii. 202. 

 Cardium corneum. Pulteney^ Dorset. 31.; Mont. T. B. 86. 



Cardium nux. Da Costa, B. S. Cyclas cornea. Lam. 

 Hist. v. 558. ; Pfeiffer, 120. t. 5. f. 12. ; Nikon, Moll. Suec. 

 96.; Turton, Biv. 248. t. 11. f. 14., Man. ed. 1. 13. f. 2.; 

 Flem. B. A. 452. ; Jenyns, 1. c. 8. ; Leach, Syn. Moll. 290. ; 

 Dupuy, Moll. Franc. 666. t. 29. f. 4. ; Forbes and Hanley, 

 B. M. ii. 113. t. 37. f. 3. 456. Cyclas stagnicola. Leach, 

 MSS. Brit. Mus., Syn. Moll. 291. Cyclas cornea (3. 

 Jenyns, 1. c. 8. Cyclas rivalis. Drap. Moll. 129. Cyclas 

 nucleus. Stud. Verz. 93. Cyclas flavescens. Macgilliv. 

 Moll. Aberd. 246. Cycl. isocardioides. Norm. Cyclas 

 citrina. Brown, III C. 132. t. 39. f. 37. 



Var. 1 . stagnicola. Shell subglobose, rather flattened on the 

 basal edge ; umbones tumid, pellucid, very prominent : 

 Tellina stagnicola. Shepp. Linn. Trans, xix. 150. 



Var. 2. gibbosa. Shell very gibbous ; margin very blunt. 



Var. 3. compressa. Shell rather compressed, the margin meet- 

 ing at an acute angle: Cyclas alata. Leach, Syn. Moll. 

 291. (?) 



Var. 4. minor. Small, nearly globular. 



Inhab. turf-pits, fens of Cambridgeshire/ 



Animal white ; the siphons rather elongate, pale 

 flesh-coloured, upper rather tapering, lower cylin- 

 drical, truncated; foot, when expanded, rather 

 longer than the shell. 



