434 



author traces the Crinoids, or Encrinites, through various strata, 

 showing the gradual disappearance of ancient forms, and their re- 

 placement by new forms of Kadiata. The chief characteristics of the 

 Crinoidea, up to the Carboniferous epoch, are, that the articulations 

 which connect the indurated pieces of which the column is composed 

 radiate by simple strige divei'ging from the central axis ; and that 

 the dorsal portion of the body, that is, the part below the rays, ge- 

 nerally preponderates over, or at least is fully equal to, the ventral 

 or upper portion. From this period these older types gradually 

 became extinct, and we find them succeeded by forms in which the 

 ventral portion is generally superior in size to the dorsal, which 

 seems now to serve only as a base for the support of the wide-spread- 

 ing rays ; while, with two exceptions (the Apiocrinus and Gnatho- 

 crinus), the articulations in the columns are secured by crenulated 

 floriform ridges on the facets of the joints. This peculiar form at- 

 tained its maximum in the Lias; since which it has dwindled down 

 to a solitary Pentacrinus, and a few other Crinoids, having little re- 

 semblance to the ancient forms. 



The author then gives a historical sketch of the various opinions en- 

 tertained regarding these animals, and notices the superstitious ideas 

 regarding them, whence had on'ginated the names given to them of 

 fairy-stones, giants' tears, St Cuthbert's beads, star-stones, wheel- 

 stones, screw-stones, &c. After alluding to the views of early au- 

 thors, he proceeds to show the advances which have been made of 

 late in our knowledge of the structure and affinities of Crinoids. 

 He traces the analogies between them and the Echinodermatous tribe. 

 From the Comatula we pass through a succession of forms onwards 

 to the most perfect Echinoderm (the sea-urchin), and backwards to 

 the Mai'supite, the Pentacrinus, and the Crinoidea. General aflBni- 

 ties exist between the free swimming Euryale and the Marsupite, 

 as well as the fixed Euryalicrinus of the Silurian and Carboniferous 

 rocks. 



The analogy between fossil Crinoids and the recent forms of Echi- 

 noidea is noticed. The author traces the gradual and uninterrupted 

 transition from the Asteriadse to the Crinoidea, from the Crinoidea 

 to the Blastoidea, from the latter to Echinida, and finally to the 

 star-fishes. 



