FAMILY 5. OSTRACEA 173 



dine adhesionis subcalcarea libere impleta ; valva superiore concava, 

 impressione musculi cartilaginibusque accessoriis duabus imbuta. 

 Ligamentum internum sub umbonibus positum. 



This genus originally included not only the Anomise of modern authors, 

 but also many of those mollusks which, on account of their peculiar 

 system of organization, have been considered as constituting two distinct 

 classes, Brachiopoda and Pteropoda. The Anomise, the Terebratulce, 

 and the HyalcBoe were associated together in one and the same genus by 

 Linnaeus from a fancied resemblance in their shells, without reference to 

 the structure and habits of their animal inhabitants ; and when their 

 anatomy, therefore, attracted the notice of scientific men, the fallacy of 

 this arrangement became manifest. It would be both frivolous and un- 

 necessary to notice the grounds upon which these important changes in 

 the classification have been established, as, on reference to the descrip- 

 tive characters of these classes, they may be at once detected. The 

 Anomias do, nevertheless, exhibit a certain indistinct transition to the 

 Terebratulce, inasmuch as they both live attached to rocks, shells, and 

 other marine debris by the aid of a muscular tendon passing through 

 a distinct orifice in the shell : here, however, the resemblance ceases. 

 Through the fibres of this tendon of adhesion which is exserted by the 

 Anomise, there is secreted, after a time, on the surface to which it is 

 affixed, a series of thin subcalcareous plates ; and when these plates 

 become amalgamated and hardened, they form what has been called the 

 stopper. This peculiarity of habit is not found in the Terebratulce ; the 

 soft parts are moreover altered in their position within the shell, besides 

 differing in many other essential particulars. By the interposition of the 

 genus Placunanomia , the Anomise are closely allied to the Placuncc ; their 

 shells are of the same fibro-laminal composition as those of the rest of 

 the Ostracea, and are often much distorted in growth. As they assume 

 the shape of any substance they happen to be in contact with, it is im- 

 possible to attach any importance, in drawing up a specific description, 

 to the regularity or irregularity of the valves. If, for example, the Ano- 

 miae become attached to a flat surface, their shells are well and regularly 



