206 MALACOZOA. TROPIOPODA. LAMELLIBRANCHIATA. 



with the umbo convex, narrowed to an obtuse decurved 

 projecting point. Cylindricus, long and round. 



7. Andmia strioldta. Shell subovate, thin, subpellu- 

 cid ; the upper valve very convex, somewhat gibbous, 

 squamoso-rugose, with radiating strioe. Strioldtus, with 

 small streaks or ridges. 



DIMYARIA. With two adductor muscles. 

 FAMILY IT. MYTILINA. 



Animal oblong, with the mantle open beneath, co- 

 herent behind, forming a single orifice ; the foot slender, 

 tongue-shaped, with a byssus at its base behind. Shell 

 regular, equivalve, very inequilateral ; the hinge tooth- 

 less ; the ligament linear and dorsal ; the anterior mus- 

 cular impression very small. Named from the genus 

 Mytilus. 



GENUS 1. MYTILUS. Shell oblong or obovate, equi- 

 valve, extremely inequilateral, convex ; the umbones 

 small, prominulous, terminal. Mytilus, a mussel. 

 Linnaeus. 



1 . Mytilus edulis. Shell ovato-oblong, extremely 

 variable in form, size, and colour. Edulis, eatable. 



A. M. edulis vulgdris. Common. 



B. M. edulis pellucidus. Pellucid. 



C. M. edulis incurvdtus. Incurved. 



D. M, edulis anguldtus. Angulate. 



E. M. edulis pusillus. Diminutive. 



GENUS 2. MODIOLA. Shell oblong or obovate, equi- 

 valve, very inequilateral, convex ; the umbones small, 

 prominulous, nearly terminal. 



1 . Modiola barbdta. Shell obovato-oblong, very con- 

 vex, more or less covered with filamentary processes of 

 the epidermis. Barbdtus, bearded. 



2. Modiola discrepans. Shell obovate, compressed, 

 anteriorly and posteriorly radiatingly striate, smooth in 

 the middle. Discrepans, discordantly marked. 



3. Modiola discors. Shell ovate, tumid, anteriorly 



