TRIBE CONCHACEA. 89 
SECTION.—LAMELLIPEDES, 
The foot depressed, lamelliform, and not posterior. 
TRIBE CONCHACEA. 
With at least three primary teeth in one valve, and the other nith 
generally the same, although sometimes with less. 
SECTION.—FLUVIATILE. 
Shells with lateral teeth at the hinge, and covered mith a spurious 
epidermis, or cuticle. 
CYCLAS. 
Ovate, globular, transverse, and equivalve, with the beaks tumid ; 
cardinal teeth very small, sometimes barely perceptible ; or with 
two in each valve of which one is complicated ; or only one pli- 
_ cated or lobed tooth in one valve, and two in the other ; lateral 
teeth transversely elongated, compressed and lamelliform ; liga- 
ment external. 
C. Rivicora * Lam. 1.—Turt. B. t. 11. f. 13.—Turt. WM. t. 
1. f. 1.—Teviina Cornea. D. p. 104.—W. t. 5. f. 90.—E. t. 
302. f. 5.— Wood. G. C. it. 46. f.3. Sub-equilateral, sub-globose, 
ovate, ventricose, rather solid, beautifully and closely striated, green- 
ish brown with two or three darker bands and the umbones obtuse, 
paler, and often circumscribed by a darker line; the edge and 
lunule yellow : cardinal ligament conspicuous. 44..31.—EKurope. 
C. Cornea.* Lam. 2.—Turt. M. t. 1.f. 2.—Turt. Bait. 
Jf. 14. p. 248.—TreLiina Cornea. Lin. 1120.—Don. t. 96.— 
Ch. f. 133.—C. Rrvauis. Drap. t. 10. f. 14. Sub-equilateral, 
sub-orbicular, globose, thin, and very finely striated transversely : 
umbones blunt : ligament not conspicuous.— Variety—Sub-globose 
and rather flattened on the basal edge: umbones tumid, pellucid, 
and very prominent.—Variety— Smaller and nearly globular. — 
Europe. 
C. Lacustris. Drap. t. 10. f.6, 7.—Lam. 3.—Turt. M. t. 
1. f. 4.—(copy). Sub-rhombic, rather flattish, very finely striated, 
and Siew Eee — Hurope. 
C. Amnica.* Turt. M. f. 5. p. 15.—Turt. B.t. 11. f. 15.— 
W. t. 3. f. 19.—Tetiina A. D. p. 105.—C. Ostrava. Lam. 
4.—C. Patustris. Drap. t. 10. f. 15,6. Inequilateral, ovate, 
ventricose, deeply striated sulcately, greenish horn-colour ; the um- 
bones rather blunt.— Hurope. 
C. Carycunata.* Lam. 5.—Drap. t. 10. f. 13, 4.—Turt. 
M. f.3.—C. Lacustris. Turt. B. p. 249. t. 11. f. 18.—Car- 
pium L. Mont. p. 89.—Teiuina L. W.t. 5. f. 91. Nearly 
