DESCRIPTION. 145 



dining to white ; hinge with a triangular sinus ; 

 upper valve turgid towards the middle, rough 

 and transversely ribbed on both sides ; lower valve 

 smaller, flat, and channeled through the middle. 

 Inhabits the Indian Ocean. 



Fig. 5. O. Isognomtim. 



Shell equivalve, lobed, the larger lobe at right 

 angles to the hinge. 



Rumph. Mus. tab. 47. I. 



Specimen inclining to violet, with shades of 

 black, within pearly ; lamellate ; beak unclosed. 



Inhabits the Indian Ocean and South Seas. 



PLATE X. 



Fig. I. Anomia vifrea. 



Shell nearly orbicular, ventricose, hyaline, ex- 

 tremely thin 'y lower valve with two bony rays at 

 the hinge, besides lateral teeth ; upper valve with 

 a prominent perforated apex. 



Born, Mus, Cces, p. 116. vign. 



Specimen very pale cinereous ; striated trans- 

 versely ; striae scarcely perceptible. The annexed 



