PLATE 39. 
1_4. Merista ( = Meristella) lasvis. 
1 a - d. Dorsal, ventral, front, and profile views of a young, very gibbous specimen of this 
species, which shows a small but very deep sinus on the ventral valve. 
2 a - e. Dorsal, profile, and front views of young specimens which are not very gibbous. 
3 a - e. Views of young individuals, only one of which shows any evidence of a mesial sinus. 
3 f t g, h, i, k. Dorsal, ventral, profile, and front views of larger specimens. The specimen 
fig. 3 g presents no emargination in front, as do the others 3 f-k. 
3 /, m, n. Front, dorsal, and cardinal views of a full-grown specimen. 
3 o, j o, r, s. Dorsal, profile, ventral, and front views of a larger specimen, showing a stronger 
emargination in front, and a mesial sinus extending nearly to the beak of the ventral valve. 
3 t, u. Dorsal and profile views of a larger individual, which has no sinus or elevation upon 
the valves. It is possible that this may prove a distinct species. 
4 a. Interior of the ventral valve. 
4 b. c, d. Casts of the ventral valve, and profile of the same. 
