SEPTIFER. 



171 



Lithophagiis phinmla^ Haiiley, 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 

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

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

 Septifcr bifitrcatiis^ Rve., Sep^-ti-fer bi-fur-ca^-tus. 

 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, 

 pearly, and sometimes beautifully tinted with purple. 

 The great Horse-Mussel, Modiola modiolus^ Mo-di'- 

 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 tw^o in breadth. 

 The epidermis is chestnut brown and is strongly 

 bearded. 



Fig. 144. 



Modiola recta^ Conrad, Straight INIussel, is shown in 

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



