40 PICTURESQUE SKETCHES 



zation extremely simple compared with that of the 

 other bivalves, together with a complexity in the 

 structure of the shell, and in the contrivances for 

 keeping the two valves partly asunder, which are 

 quite peculiar to them. The shell, too, is generally 

 laminated, or even fibrous in its texture : numerous 

 long hairs seem to have passed, in some cases, from 

 the plates, while in others they passed through 

 the plates of which the shell is made up. Nothing 

 can well be imagined more varied than the contri- 

 vances by which the ancient species of this group 

 were enabled to obtain existence. 



The two valves of brachiopodous shells are not con- 

 nected by any hinge ; but the lower valve was either 

 directly fastened to a rock or some marine substance, 

 or a bundle of fibres or hairs passed through one valve 

 from the other, and were collected into a pedicle or 

 foot- stalk, by which the animal could attach itself at 

 will. Two arms, or tentaculae, were wound in a 

 spiral within the shell when at rest, but were capa- 

 ble of being expanded in search of food ; and these 

 being covered with cilia those peculiar hair-like ap- 

 pendages frequently met with in animals of imperfect 

 organization powerful currents were produced in the 

 surrounding water, which being directed towards the 

 mouth as a focus, would hurry into that aperture 

 whatever nutritive particles might chance to be in the 

 vicinity/"" The food of these creatures consisted 

 probably of the minutely divided and decomposed 

 particles of dead animals of various kinds floating 

 about in the seas ; and different species seem to have 

 been enabled to live at various depths, varying from a 



* Rymer Jones's Animal Kingdom, p. 365. 



