SOME NEW DEVONIC FOSSILS 



217 



greatest elevation along the anterior crescence line and the slope 

 thence gradual in all directions except anteriorly, where it is curved 

 down and inward. The general expression of the shell will be better 

 appreciated from the figures than by description. There are large 

 and small shells present with these characters all representing 

 the same specific form. 



The hinge characters are excellently shown in one specimen of 

 the left valve. The beak is terminal ; beneath it is the apex of 

 the broad ligament area which is strongly striated transversely. 



Mytilarca dalhousie 



The anterior edge of this area slopes obliquely back to the inner 

 apex of the valve and at this point is a single oblique elongated 

 tooth, doubly crenulated on the crest leaving between it and the 

 edge of the ligament area a pit or socket for the reception of the 

 tooth of the other valve. This socket is bounded below by a 

 continuation of the tooth. Toward the posterior end of the hinge 

 is an oblique but obscure ridge below the ligament area. This 

 hinge structure is in agreement with Hall's delineation of it for 

 the genus Mytilarca. The umbonal region of the shell is thick 

 and the posterior margin shows successive thickened layers of 

 shell growth. 



Lower Devonic. Dalhousie, N. B. 



Modiomorpha impar nov. 



Shell of small or medium size with straight hinge line not ex- 

 tending for the full length of the valves. Beaks anterior but not 

 terminal, depressed, the umbonal region rising gradually and soon 

 broadening out over the low posterior slope. In front of this ridge 



