346 HIARINiE. 



Genus MACHA, Oken. 



Siphons very large, united at the base, free at the ends, 

 branchial orifice fringed, anal plain. 



Shell transversely oblong, compressed, rounded and gaping 

 at the extremities, more or less invested with an epidermis, 

 beaks sub-central, margins nearly parallel. Hinge with two 

 diverging primary teeth in each valve ; ligament prominent. 

 Anterior muscular impression lobed; pallial impression 

 deeply sinuated. 



Sy?i. Solecurtus, Blainv. Solenocurtus, Soiv. Psam- 

 mosolen, Bisso. Cyrtosolen, Herrm. 



Ex. M. Candida, Benieri, pi. 93, fig. 4. Shell, M. stri- 

 gillata, Linnceus, fig. 4, a, 4, b. 



The animal of Macha is very large, and is not entirely 

 retractile within the shell, the margin of the mantle protrud- 

 ing, especially when the cavity is distended with water. The 

 species usually bury themselves in sand, in the coralline 

 zone, beyond low-water mark, and in consequence are diffi- 

 cult to procure in a living state. Two species are inhabitants 

 of the shores of the British Islands. 



Species of Macha. 



alba, Martyn. solida, Gray. 



Candida, Benieri. strigillata, Linn. 



exarata, Phil. 



