466 foett-fifte report on tee 8 tate museum. 



Color. 

 The shells of most, living species are of light or neutral tints, 

 white or horn-color. The deep-sea, species are usually vitreous, 

 translucent and very thin-shelled. A deep orange-red in radiating 

 bands or in solid tints, colors some species (Terebratulina, 

 Kraussina, etc.) ; light yellows, deep and light shades of green 

 (Lingula), black in bands (Crania) or masses (Rhynchonella) 

 embellish these shells. Even among the fossil species traces of 

 faded color-marks are occasionally observed ; Deslongchamps 

 has described them among Jurassic species, Davidson among the 

 Carboniferous, and Kayser has found a color-marked Khyhchon- 

 ella in the Devonian. The large, highly ornamented species of 

 Palaeozoic times, with their external sculpture heightened by a 

 brilliant coloring must have been objects of exquisite beauty. 



The Shell. 

 External Form and Terminology of its Parts. 



The brachiopod shell assumes a great variety of forms. Usu- 

 ally both valves are more or less convex, but they may be almost 

 flat, and one of them is frequently concave, following the curva- 

 ture of the other. In early age the surface of all is normally 

 smooth, and while many retain this smoothness throughout their 

 existence, the greater number bear radial ribs or plications, or a 

 series of concentric varices and growth-lines. 



The valve, which, in youth or maturity, bears at or near its 

 apex, a perforation or fissure, is known as the pedicle-valve, as it 

 is through this opening that the pedicle or fleshy arm of attach- 

 ment is protruded, being attached to the inner surface of the 

 valve by a series of muscular bauds. This valve has ako been 

 quite generally known as the ventral, as it may, from certain 

 considerations, be regarded as lying on the ventral side of the 

 animal. It is usually the larger of the two valves, and lias, 

 therefore, been designated by many writers as the larger valve ; 

 but there is so great a number of instances in which the pedicle- 

 valve is not the larger, that this term is objectionable. This 

 valve bears the teeth or the principal articulating apophyses of 

 the hinge, and has hence been termed the dental valve ; an unsatis- 

 factory designation, as a, vast number of species is provided 

 with no such apparatus. A few writers have called it the neural 



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