SEPTIFER. 



I 7 I 



Lithophag2is plumula, Hanley, Lith-of'-a-gus plu'- 

 mu-la, has a small, cylindrical shell, rounded in front 

 and tapering behind. It is a borer, as its name, the 

 Rock-eater, would indicate; and it is found sometimes 

 iu rocks, and sometimes in old shells. It has a light 

 brown epidermis, and is an inch or two in length. 



Septifer bifurcatus, Rve., Sep'-ti-fer bi-fur-ca'-tus, 

 Fig. 144. Its generic name means the Partition- 

 bearer, and was given from the fact that 

 a little shelly partition is stretched across 

 a small part of the interior of each valve, 

 near the umbo. The specific name, 

 meaning two-forked, applies to the branch- 

 ing external ribs with which the surface 

 of the valves is covered. The shell is 

 strong, somewhat wedge-shaped, and is 

 covered with a dark epidermis. The interior is white, 

 pearh*, and sometimes beautifully tinted with purple. 

 The great Horse-Mussel, Modiola modiolus, Mo-di r - 

 o-la mo-di'-o-lus, is most abundant in northern waters. 

 Shell somewhat cylindrical, very large and full; 

 sometimes four inches in length and two in breadth. 

 The epidermis is chestnut brown and is strongly 

 bearded. 



Fig. 145 



Modiola recta, Conrad, Straight Mussel, is shown in 

 Fig. 145. The shell is long and narrow, thin and 



