252 
CYCLAD^. 
ropods^ they contrive to traverse the vessel from 
side to side, as though they were crawling along a 
solid plane. 
1. Cyclas Lam. (Cycle.) 
Animal with suborbicular mantle produced behind 
into two elongate contractile siphons ; foot 
tongue-shaped, very extensile; shell suborbi- 
cular, nearly equilateral ; hind teeth minute, one 
in the right and two in the left valve ; lateral 
teeth compressed, elongate, lamellar. 
The shells are known from Pisidium by their being 
rounder and more equilateral. 
a. Cardinal teeth two^ diverging^ well developed ; shell 
rounded^ and not channelled at the umbones. 
114. 1. Cyclas rivicola. River Cycle. — Shell sub- 
globose-ovate, ventricose, rather solid, beauti- 
fully and closely striated, greenish brown, 
with two or three darker bands ; edge and 
lunule yellow ; umbones obtuse ; cardinal 
ligament conspicuous, (t. 1. f. 1.) 
Tellina cornea, p, Maton and Hacket^ Linn. Trans, viii. 59. ; 
Turton., Conch. Diet. 180.; Wood., t. 46. f. 3. — Cyclas 
cornea, a. Drop. Tabl. — Cardium corneum, var. Montagu., 
T. B. 86. — Cyclas cornea, a. Drap. Hist. Moll. 128. t. 10. 
f. 1. 3. — Cardium amnicum. Dorset. Cat. 32. — Cyclas rivicola. 
Leach., in Lam. Hist. v. 558.; Pfeiffer., L. and W. 121. t. 5. 
f. 3. 5.; Turton., Bivalves, 248. t. 11. f. 13. ; Fleming, Brit. 
Anim. A52.-, Jenyns, Trans. Camh. P. S. 6.; Turton, Man. 
ed. 1. 12. f. 1.; Leach, Syn. Moll. 289. ; Dupuy, Moll. Franc. 
665. t. 29. f. 3.; Forbes and Hanley, B. M. ii. 111. t. 37. 
f. 12. t. 2. £ 1. — SphsBrium riviculum. Mont. Cat. ii. 30. — 
Spii. rivicola. Bourg. in Amden, 6. 1. ; Bourg. Mon. 12. 
Young, compressed, pale. 
Cyclas sequata. Sheppard, MSS. Brit. Mus. 
Inhab. rivers Thames, Trent, &c. 
