‘192 Mrs. Sheppard on 
most wholly internal ; one sublateral, muscular, elongated 
impression, axe shaped.” 
Modiola plicatula, ‘shell oblong, towards the outside ob- 
liquely dilated ; longitudinally sulcated ; inside edge waved.” 
Common near the Gulf, likewise met with higher up thé 
river; the shell is white, covered with a brown, or yellow 
epidermis. 
Mytelus. 
‘Shell longitudinal, equivalve, regular, pointed at the base, 
fixed by a byssus ; beaks almost strait, terminal pointed.—~ 
Hinge lateral, usually without teeth, ligament marginal, sub- 
interna). One large clavate muscular impression.” 
The Modiole formerly belonged to this genus, but were 
removed from it by Bruguiere. 
Mytelus borealis, ‘Shell oblong, whitish bluc, epidermis 
black, beaks incumbent divaricate.” Inhabits several parts of 
the St, Lawrence : the shell is of a solid and flinty texture ; 
the beaks rather one sided, There is likewise a variety of 
this species found below Qnebec, more pearly and sometimes 
obsoletely rayed, with the inside white and shining: both 
these shells are often brought up with Qysters, 
Osrracea, Firru Famity? 
Few of this family are to be met with here, the only one 
which has come within my observation is the well known 
Ostrea. 
‘¢ Shell adhering, inequivalve, irregular ; beaks distant, be- 
coming very nnequal by age. Hinge without teeth ; ligament 
internal, or partly so. Pit and beaks of the lower valve in- 
creasing by age, sometimes to a great length.” The animals 
remain fixed to maritime bodies, and have no other motion 
than that of opening and shutting their valves to receive what- 
ever nourishment the waters may bring them. 
Ostrea canadensis, ‘‘shell elongated rather bent, broadish 
above, Jamelated,thick, inferior valve conyex.’’ Inhabits the 
mouth of this river, sometimes grows to the length of eight 
inches, TWELFTH 
