CYCLAS. 257 



b. Cardinal teeth single (rarely two divergent) ; shell 

 thin, subquadrigonal ; umbones prominent. 



us. 5. CYCLAS lacustris. Capped Cycle. Shell 

 rather rhombic, compressed, thin, yellowish 

 white, diaphanous ; umbones prominent, 

 rather acute, and tuberculose ; ligament 

 inconspicuous, (t. 1. f. 3.) 



Cardium lacustre. Mont. T. B. 89. Tellina lacustris. Linn. 

 Trans, vii. 60.; Turton, C. D. 180. Cyclas calyculata. 

 Drop. 130. t. 10. f. 13, 14. ; Lam. Hist. v. 559. ; Pfeiffer, 

 122. t. 5. f. 17, 18.; Nilson, 99. ; Turton, Man. ed. 1. 14. 

 f. 3. ; Dupuy, Moll. Franc. 672. t. 24. f. 8. ; Forbes and 

 Hanley, B. M. ii. 118. t. 37. f. 7., t. O. f. 7. Cyclas lacustris, 

 Turton, Biv. 249. t. 11. f. 18.; Leach, Syn. Moll. 289. 

 Tellina tuberculata Alten, Syst. 4. t. 1. f. 1. Cyclas tu- 

 berculata. Klees, 45. Sphseriuni lacustre. Bourg. Sphcer. 

 36. Sphaerium Brochonianum. Bourg. Sphcer. 50. t. 3. f. 

 5. Cyclas consobrina. Feruss. in Blainv. D. S. N. xii.. 

 279. Sphaerium Deshayesianum. Bourg. Amcen. 6. Sphae- 

 rium ovale. Bourg. Sphcer. 31. t. 4. f. 6. 10. Cyclas la- 

 custris. Forbes and Hanley, B. M. ii. 118. 



Young, the apex of the shell large relatively to the size of the 

 specimen. 



Inhab. rivers. 



Var. 1., shell orbicular, less compressed, subdiaphanous, red- 

 dish brown. ^ 



Cyclas lacustris. Alder, Cat. i. 40., Brit. Mus. Cyclas 

 calyculata j3. Jenyns, Monog. 11. 



Inhab. ponds. 



Var. 2., shell orbicular, rhombic, rather ventricose, subdiapha- 

 nous, reddish; umbones less prominent, blackish. 



Cyclas stagnicola. Leach, MSS. fide Lam. Cyclas caly- 

 culata, var. 2. Lam. Hist. v. 559. Cyclas calyculata y. 

 Jenyns, Monog. 11. 



Inhab. north of England. (Jenyns.) 



Animal white ; siphons white, elongate. 

 This species, when in confinement, shows more 

 activity than C. cornea ; they sometimes remain at 



