206 MALACOZOA. TROPIOPODA. LAMELLIBRAXCHIATA. 



with the umbo convex, narrowed to an obtuse decurved 

 projecting point. Cylindricvs, long and round. 



7. Anomia 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. — Mttilina. 



Animal oblong, with the mantle open beneath, co- 

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

 tongue-shaped, ^At\\ 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. Mttilus. — Shell oblong or obovate, equi- 

 valve, extremely inequilateral, convex ; the umbones 

 small, prominulous, terminal. Mytilus, a mussel. 

 Linnseus. 



1. Mytilus edulis. — Shell ovato-oblong, extremely 

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



A. M. edulis vulgaris. Common. 



B. M. edulis pellucidus. Pellucid. 



C. M. edulis incurrdtus. Incm-ved. 



D. M, edulis angiddtus. Angnlate. 



E. M. edidis 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. Barhdtus, bearded. 



2. Modiola discrepans. — Shell obovate, compressed, 

 anteriorly and posteriorly radiatingly striate, smooth in 

 the middle. Biscrepans, discordantly marked. 



3. Modiola discors. — Shell ovate, tumid, anteriorly 



