ARCIN/R. 533 



Sub-fam. AKOINiE. 



Gills sub-pinnate, separate from each other behind. A 

 byssal groove at the base of the foot. 



Shell with the hinge-margin straight ; cartilage in small 

 marginal pits. 



Genus ARC A, Liimseus. 



Shell oblong, sub-quadrate, gaping in front ; surface of 

 valves covered with a paleaceous epidermis ; beaks remote. 

 Hinge-margin somewhat produced at the ends; teeth 

 divided into numerous small, nearly equal-sized crests ; 

 ligament external; the ligamental area broad, lozenge- 

 shaped, with a series of distant cartilage-grooves con- 

 verging from the hinge-margin towards the beaks. Pallial 

 impression entire ; muscular scars very marked. 



Sy?i. Daphne, Daphnoderma, Poll. Navicula, Blaitiv. 

 Cibota, Browne. Byssoarca, Swains. 



Ex. A. Nose, Liwueus, pi. 124, fig. 3. Shell, A. Noae, 

 fig. 3, a, 3, b. 



The species of Area are not very numerous, and are 

 found chiefly in tropical seas; one is a native of Britain. 

 They often anchor themselves by means of a strong byssus 

 to rocks and stones, or conceal themselves in holes and 

 crevices. 



