88 JOURNAL OF THE NEW JERSEY 



D. Twice aa long as high 2. Modiola. 



D. Less than twice as long as high 4. Crenella. 



1. Myti£us, L. 



Shell wedge-shaped, rounded behind, usually smooth ; umbones 

 terminal, pointed ; hinge teeth minute or none. 



Animal with the mantle margins plain behind and slightly 

 projecting ; byssus strong and coarse. 



1. Mytilus edulis, L. (Fig. 2.) Shell ovate-triangular, um- 

 bones pointed and placed at the end of the shell; basal and 

 hinge margins nearly straight ; gonial ridge distinct. Color of 

 shell itself violet to horn color ; epidermis usually blue-black ; 

 within, silvery white except the margins which are violet ; some- 

 times the colors radiate from the umbo. L. 75 ; H. 35 ; W. 30 ; 

 An. of margins 50°. — Whole coast. Common on rocks and tim- 

 bers. 



2. Modiola, Lam. 



Shell oblong, inflated in front; umbones near the anterior end, 

 obtuse ; hinge toothless. 



* No radiating ribs, sometimes with faint radiating lines /. 



* With radiating ribs 2. 



1. Modiola modiolus, L. Shell oblong-ovate; umbones tumid 

 and placed on one side near but not at the anterior end ; basal 

 margin arched ; gonial ridge broad, rounded ; shell compressed 

 along hinge margin ; radiating lines faint or none. Epidermis 

 thick and leathery, chestnut or brown in color ; interior pearly, 

 of a somewhat livid color. L. 100 ; H. 50 ; W. 45 ; An. of 

 margins 45°. Sometimes L. 180. — New Jersey and north. Com- 

 mon ; thrown on beach from deep water. 



2. Modiola plicatula, Lam. Shell quite elongated ; umbones 

 as in the preceeding ; surface ornamented with numerous radiat- 

 ing ribs ; these are most conspicuous above and behind ; they 

 are very fine in the podial region. Epidermis greenish-yellow 

 to reddish-brown ; within pearly, more or less purple tinted. 

 L. 75 ; H. 30 ; W. 23 ; An. of margins 30°. Sometimes L. 100.— 

 Whole extent. Very common on mud of tide water flats. 



3. MoDiOLARiA, Beck. 

 Shell rhomboidal, ornamented with two sets of rather fine, 

 radiating lines, the middle portion smooth. 



1. Modiolaria nigra, Gray. Shell ovate, widest behind ; the 



