10 TEREBRATULIDjE. 



* Jointed. 



Family I. TEREBRATU'LID.E, Gray. 



Body oval : arms folded back, and supported either by shelly 

 processes issuing from the hinge of the lower valve, or by lon- 

 gitudinal septa or partywalls in that valve : attachment formed 

 by a peduncle, which passes through a hole in the upper valve. 



Shell longitudinally or transversely oval, more or less con- 

 vex : skeleton or apophysary system consisting of riband-shaped 

 plates, which are frequently looped or united : hinge formed of 

 two side-teeth in the upper valve, which lock into sockets in 

 the lower valve : muscular scars slight and seldom visible. 



This family is very numerous and diversified in cha- 

 racter, and it is also widely dispersed both in space and 

 time. Some of its members occur in every sea, from 

 the arctic to the antarctic pole ; and its geological 

 range appears to include all the known strata, from the 

 Silurian to those which are now in course of forma- 

 tion. Colonna in 1616 was the first to use the name 

 Anomia, and applied it to species of Terebratula j and 

 Linne and other naturalists of the old school also placed 

 them in the former genus, because they are attached to 

 extraneous substances by a fibrous tendon passing 

 through one of the valves of the shell. But although 

 the analogy holds good to a certain extent, it is not 

 complete. In this section of the Brachiopoda the upper 

 valve, and in Anomia the lower valve is thus perforated, 

 to say nothing of the very different organization of the 

 animal and internal structure of the shell. Systematists 

 are not yet agreed as to the number of genera into 

 which this large family ought to be divided, nor whether 

 any or how many subgenera are allowable. Either mode 

 of distinction, however, is clearly artificial, and used 

 merely for the sake of convenient classification. As 



