The Cambridge natural history . ched to a water-logged piece of wood, fromthe Clyde area. stalk protrudes. This aperture may he completed by the ventralshell, or the latter may only be notclietl, in whicli case the holeis completed by the posterior edge of the dorsal shell. The nature of the shell has been used in classifying thegroup into two orders :— I. The Ecardines, whose shell is chitinous l)ut slightly strengthened by a deposit of calcareous salts. Thereis no hinge and no internal supports for the alimentary canal terminates in an anus. II. The Testicardines, whose shells are c
The Cambridge natural history . ched to a water-logged piece of wood, fromthe Clyde area. stalk protrudes. This aperture may he completed by the ventralshell, or the latter may only be notclietl, in whicli case the holeis completed by the posterior edge of the dorsal shell. The nature of the shell has been used in classifying thegroup into two orders :— I. The Ecardines, whose shell is chitinous l)ut slightly strengthened by a deposit of calcareous salts. Thereis no hinge and no internal supports for the alimentary canal terminates in an anus. II. The Testicardines, whose shells are composed of calcareous spicules. The valves are hinged together, and there is usually an internal skeleton su|)porting the arms. There is no anus. The outside of the shell of recent Brachiopods is often smooth, but many are ridged. In a recent species, lUtynchonella Dodcr- leini from Japan, Davidson ^ has described a number of spines ^ On a living Spinosc PJiynclioncUa from Japan, Ann. Mag. Nat. Hist., 5thscr. vol. xvii. XVII COLOUR 467 arranged in concentric circles on the ril)bed shell. They are notso long- as the spines irregularly scattered on the shell of from tlie Jurassic forniations. Some shells are brightlycoloured, as, for instance, the various species of Cistella whichlive on the coralline rock in tlie Mediterranean ; these exhibiti) or rays of alternate orange and briglit pink. On theother hand, the shells of Terelwatula mlrea are t)f a slightly trans-lucent white, and of the utmost delicacy. They are very Lirge,so that tlie cavity within tlie valves is of much greater size thanthe body of the animal, but in otlier genera the S(^ft parts arepacked very closely, and there is but a very small mantle-cavityor space within the shell unoccupied by the body of the is, however, more common for the shells of Urachiopods to l)eof a dull yellowish colour, and to be somewhat massive. Mostspecies are attached by a pedicle or stalk to some roc
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
