CYCLAS. 253 



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

 bones paler and often circumscribed with a dark line ; 

 length 10^, height 8|, 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. \m. 59. ; 

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

 398.; Bourg. Spar. 21. — Cyclas scaldlana. Norm. Cycl. 

 5. t. 5. f. 12. — Sphffirium scalilianuin. Norm. Cycl. t. 1. 



— SphaBrium citrinum. Norm. Cycl. — Nux nigella. Humph. 

 Cat. 59. — Tellina rivalis. Miillcr, Verm. Hist. ii. 202. — 

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



— Cardiiun mix. Da Costa, B. S. — Cyclas cornea. Lam. 

 Hist. V. 558. ; Pfeiffer, 120. t. 5. f. 12. ; Nihon, Moll. Suec. 

 96.; Turton,Biv.2^i.i.n.i. \A., 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 staunicola. Leach, 

 MSS. Brit. 3Ius., Syn. Moll. 291. — Cyclas cornea jS. 

 Jenyns, 1. c. 8. — Cyclas rivali.'^. Drop. Moll. 129. — Cyclas 

 nucleus. Stud. Verz. 93. — Cyclas flavescens. Blacgilliv. 

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

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



Var. ] . 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 veiy 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 

 lonsrer than the shell. 



