MYTILACEA. MOLLUSCA. MODIOLA. 123 



bridges and other submerged structures, in shallow inlets with a 

 pebbly bottom, and especially on rocks not far from high-water mark, 

 clinging in immense crowds of all sizes, colors, and figures ; some 

 beautifully radiated, some dark blue-black, and others light horn-color; 

 some beautifully smooth, regular, and glistening, others distorted, rough, 

 and dingy ; the whole surface of the young shell is beset with a bristly 

 beard. While, like the M. plicdtula, it clusters about the shore, it does 

 not, like that, bury itself in the mud, but is always exposed and at- 

 tached to some solid body. It is common to find it wedged in among 

 the rocks and crevices of such shores as Nahant and Cape Ann. 



Genus MODIOLA, Lam. 



Shell oblique, wedge-shaped ; beaks very near the anterior end ; 

 hinge as in My'tilus ; impression of the mantle irregular. 



MODIOLA MODl'OLUS. 



Shell oblong-ovate, gradually widening from before backioards ; 

 hinge margin ascending, straight for about half the length of the 

 shell ; beaks tumid, obtusely angular ; epidermis dark chestnut- 

 color. 



State Coll., No. 162. Soc. Cab., No. 1973. 



My'tilus modiolus, Lin. ; Syst. Mat., 1158. Pennant ; Brit. Zool., iv. 239, t. 69. 



Montagu ; Test. Brit., 163. Chemn. ; Conch., viii. 178, t. 85, f. 759. Knorr ; 



Vergn., iv. t. 15, f. 3. Lister; Conch., t. 1057, f. 5. Dillwyn ,; Catal.,i. 



314. Wood ; Index, pi. 12, f. 31. Lin. Trans., viii. 107. Donovan ; Brit. 



Shells, pi. 23. 

 Modiola modiolus, Turton ; Brit. Biv., 199, pi. 15, f. 3 (young). Conch. 



Diet., 111. 

 My'tilus Papuanus, Deshayes ; Encyc. Meth., Vers, ii. 564, pi. 219, f. 1. 

 Modiola Papuana, Lam. ; An. sans Vert., vii. 17. Blainv. ; Malacol., pi. 64, f. 3. 

 Modiola vulgaris, Fleming ; Brit. Anim., 412. 

 My'tilus barbatus, Lin.; Syst. Nat., 1156. Donovan; Brit, Shells, pi. 70. 



Montagu ; Test. Brit., 161. Pennant ; Brit. Zool., iv. 238, pi. 67, f. 2. 



Shell large, thick, coarse and solid, ovate-oblong ; beaks placed 

 at one side, points inclined outwards, and projecting nearly as far 

 as the anterior extremity, which is very short and narrow ; the 

 upper edge is ascending, and straight about one half the length of 

 the shell, when it curves gently downwards to the posterior ex- 

 tremity, which is obtusely rounded ; the basal margin is somewhat 

 arched upwards, and at the arched portion the shell is gaping for 



