PLATE XL 



PAG* 



Fig. 57. OSTREA BOURGKOISII. Natural size. 33 



57 a. Hinge. 



Fig. 586. Upper valve of O. ATT WOODI i ? Natural size. 34 



Fig. 59. OSTREA VKATCHII. 34 



From a small and unusually thin specimen. 



Fig. 61. OSTREA CERROSENSIS. Natural size. 35 



