NO. 1 



SOOT-RYEN : THE FAMILY MYTILIDAE 



59 



right one, shell color often red in dried 



specimens, dorsal part of inside usually 



dark colored 



Periostracum with smooth hairs, usually 



equivalve 



2. Umbones inflated, twisted downward 

 and outward, protruding beyond the an- 

 terior margin 



Umbones less inflated and twisted, never 

 protruding beyond the anterior margin 



3. Anterior margin protruding for a con- 

 siderable distance beyond the umbones, 

 the anterodorsal margin with a narrow 

 lunule and forming a sharp keel toward 

 the umbones, dorsal margin straight 

 Anterior margin only slightly protrud- 

 ing beyond the umbones, the lunule 

 rather broad, anterodorsal margin not 

 forming a sharp keel and dorsal margin 

 curved 



4. Posterodorsal angle sharp (120°-140°), 

 shell relatively short, the height meas- 

 ured perpendicularly to the hinge line 

 distinctly more than half the length 

 of the hinge line 



Posterodorsal angle rounded, shell more 

 elongate, the height measured perpen- 

 dicularly to the hinge line half the 

 length of the hinge line 



5. Shell triangular, posterodorsal angle 

 about 120°-130°, posterodorsal part red 

 Shell rhomboidal, posterodorsal angle 

 about 140°, posterodorsal part brown- 

 ish-yellow 



6. Anterior part typically pouting, form- 

 ing a small but distinct narrow lobe, 

 the margin bent considerably outward, 

 shell thin, inside margaritaceous 

 Anterior part more or less broadly 

 rounded 



capax (Conrad) 



fornicatus (Carpenter) 



rectus (Conrad) 

 eiseni Strong and Hertlein 



neglectus n. sp. 

 sacculifer (Berry) 



