280 CONCHIFERA. 



Young, compressed, pale. 



Cyclas aequata. Sheppard, MSS. Brit. Mas. 



Inhab. river Thames, Trent, &c. 



The shell is rather solid, blunt within ; the umbones 

 paler, and often circumscribed with a dark line ; 

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



113. 2. Cyclas cornea. Horny Cycle, (t. 1. f. 2.) 

 Shell suborbicular, globose, thin, very finely stri- 

 ated ; umbones blunt ; ligament inconspicuous. 



Tellina cornea. Linn. S. N. i. 1120. ; Linn. Trans. 

 viii. 59. ; Don. B. S. t. 96. 



Nux nigella. Humph. Cat. 



Tellina rivalis. Miiller, Verm. Hist. ii. 202. 



Cardium corneum. Mont. T. B. 86. 



nux. Da Costa, B. S. 



Cyclas cornea. Lam. Hist. v. 558.; Pfeiffer, 120. 

 t. 5. f. 12.; Nilson, Moll. Suec. 96.; Turton, 

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

 Flem. B. A. 452. ; Jenyns, 1. c. 8. 



Inhab. rivers, ponds, and ditches. 



Var. 1. stagnicola. Shell subglobose, rather 



flattened on the basal edge; umbones tumid, 



pellucid, very prominent. 

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

 Cyclas stagnicola. Leach, MSS. Brit. Mus. 



cornea (3. Jenyns, 1. c. 8. 



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



blunt. 

 Var. 3. compressa. Shell rather compressed; the 



margin meeting at an acute angle. 

 Var. 4. minor. Small, nearly globular. 

 Inhab. turf-pits, fens of Cambridgeshire. 

 Animal white ; the siphons rather elongate, pale 



