PLATE XCII. 
I, 2. Thetis Major. ( Large Thetis .) Orbicular, convex ; beaks produced, central, incurved, approximate ; posteriorly 
angular; surface smooth. 
3, 4, 5. T. Minor# (Small Thetis.) Gibbose; beaks pointed, approximate, incurved; margin plain; posteriorly 
rounded. 
6, 7. Lutraria Carinifera. (Reeled Lutraria .) Transversely oval, convex; surface, with longitudinal strice ; pos¬ 
teriorly truncated, smooth, defined by obtuse keel. 
8, 9. L. Striata. (Striated Lutraria .) Transversely oval, compressed; posterior side small, pointed, gaping; beaks 
prominent; surface, with many, concentric strioe. 
10. L. Gibbosa. (Gibbous Lutraria.) Transversely elongated, gibbous; sides rounded; beaks depressed; surface 
smooth, with strong, concentric lines of growth; posteriorly a few, remote radiations. 
II. Mya Laeviuscula. (Smooth Mya .) Transversely oblong, squarish ; with depression from beaks to base in centre 
of valves; beaks prominent; sides rounded; surface smooth, with a few, transverse wrinkles. 
1^* Decurtata. (Divided Lutraria .) Transversely oblong, elongated; beaks obtuse, incurved; sides rounded; 
surface, with strong, transverse sulci below beaks; disc, divided by strong line of growth. 
13. M. Mandibula. (Sato Mya.) Transversely elongated, gibbose; disc flattened; anteriorly square, gaping; aperture 
oblong; surface, with about twenty-five, transverse undulations; beaks pointed, incurved. 
14. L. Elliptica. (Elliptical Lutraria .) Transversely oblong-ovate, compressed; longer side, with shallow groove 
from beak to basal line, crossed by strias-like lines; surface, with fine, concentric striae and a few wrinkles. 
15. L. Primseva. (Primceval Lutraria.) Transversely elongated, squarish, twisted; beaks tumid; posteriorly flat¬ 
tened above, curved below ; back and basal lines parallel; surface, with concentric strioe and faint lines of growth. 
16. L. Rotundata. (Bounded Lutraria.) Transversely ovate; beaks obtuse, incurved; sides narrowed ; surface, with 
strong lines of growth. 
17. L. Donaciniformis. (Donax-shaped Lutraria.) Transversely oblong-ovate, convex; with ridge from obtuse 
beaks to base ; surface smooth, with strong lines of growth ; basal line straight. 
18. M. Dilata. (Dilated Mya.) Transversely elongated, twisted; posteriorly dilated, truncated, acute; beaks sub¬ 
central, recurved; basal line straight. 
19. L. Compressa. (Compressed Lutraria.) Transversely sub-ovate; beaks obtuse; posteriorly acuminated; surface 
with transverse, striae-like wrinkles; pallial impression large. 
20. M. ASquata. (Equal Mya.) Transversely oblong-ovate; beaks central, obtuse; sides rounded; surface smooth. 
21. M. Phasiolina. (Little Pheasant Mya.) Elliptical; sides equally rounded ; beaks obtuse; surface smooth. 
22. M. Rotundata. (Bounded Mya.) Transversely oblong, convex; beaks obtuse; posteriorly rounded; surface, 
with transverse wrinkles. 
23. M. Arenaria. (Sand Alya.) Transversely ovate; anteriorly pointed; surface, with concentric sub-strise and 
undulations. 
24,25. M. Ovalis. (Oval Alya.) Transversely ovate; posteriorly pointed; surface, with concentric strioe and well- 
marked lines of growth. 
26, 27, 28, 29. M. AngUStata. (Narrowed Mya.) Transversely elongated; valves unequal; shell thin, antiquated, 
compressed ; sides obtuse, gaping; base of right valve concave; beaks small. 
30. Potomomya Subangulata. (Sub-angulated Potomomya.) Transversely oblong-ovate, compressed, equilateral ; 
anteriorly angulated, acuminated, gaping; front emarginate; cardinal tooth large; surface smooth. 
31. P. Plana. (Plain Potomomya.) Ovate, depressed, equilateral; anteriorly elongated, gaping, truncated; front 
rounded ; beaks depressed, obtuse ; surface smooth, polished internally. 
32. Lysianassa Anguilifera. (Angled Lysianassa.) Transversely elongated, gibbose; anterior side broad, gaping; 
surface, with obtuse, angularly-bent ridges ; beaks produced, obtuse. 
33. L. Literata. (Lettered Lysianassa.) Transversely elongated, sub-equilateral, convex; surface smooth, with obtuse, 
angularly-bent ridges ; shell thin. 
34. L. V Scripta. (Letter Y Lysianassa.) Transversely elongated, sub-equilateral, convex, smooth, with obtuse, 
angularly-bent ridges; angles of ridges acute. 
( HI ) 
