MYOCHAMA. 



Shell inequivalve, irregular, adhering by the external 

 surface of one valve i this attached valve has two unequal 

 diverging marginal teeth at the hinge, which are separated 

 at the umbo by the triangular pit in which one end of the 

 testaceous appendage above-mentioned is inserted, and 

 connected by a horny cartilage : the free valve, which is 

 larger than the other and very convex, has two small un- 

 equal, diverging teeth close under the umbo, in which by 

 means of a cartilage is inserted the other end of the tes- 

 taceous appendage. The umbo of the free valve is curved 

 inwards, that of the attached valve outwards. There are 

 two muscular impressions in each valve, which are nearly 

 orbicular, distant and lateral. The muscular impression 

 of the mantle has a short broad sinus. 



Only one species of this remarkable Genus has yet 

 been found, it has distinct radiating, and rather prominent 

 dichotomous ribs or grooves passing from the beak towards 

 the margins 3 these appear to be characteristic; but when 

 attached to Trigonia these natural ribs are crossed by 

 others, caused by the granose ribs of the Trigonia, their 

 position and strength depending upon the situation it 

 occupies. This species has been named Myochama ano- 

 mio'ides by Mr. S. Stutchbury; it has a thin pellucid 

 epidermis. 



