PLATE 41. 



ruga 



Fig. I a - t. Merista ( = Meristella) arcuata. 249 



I a, b. Doisal and cardinal views of a young siMJciinen. 



1 c, d, e,f. Dorsal, vcutral, and profile views of large specimens. 



1 g, h, i, k, I. Dorsal; ventral, profile, and front views of full-grown individuals, showing tlie 

 forms of well-preserved specimens. 



1 m, n. Dorsal and profile views of a very gibbons form, which is unusually extended laterally. 



1 0. Interior of a ventral valve. 



1 p. Cast of the beak of the ventral valve. 



1 t. An imperfect specimen which has been eroded at the sides, showing the internal spires. 



Fig. 2 a - g. Casts of Meeista ( = Meristella) : Probably of M. arcuata. 250 



2 a. Cast of the dorsal valve. 



2 6. Cast of the ventral valve, showing the muscular impressions and extended process which 

 filled the beak of the shell. 



2 c, d. Casts of the ventral valve, showing some differences in the form of the muscular im- 

 pressions, and the portions filling the cavity of the beak. The radiating striae arc partially 

 preserved on fig. 2 c. 



2 e. Cardinal view of a well-preserved cast. 



2/, g. Profile views of 2 d and 2 c respectively; the specimens 'Z c, g preserving the cast of 

 both valves, i d,f being the ventral valve only. 



