276 NATURAL HISTORY. 



about after the visceral mass has fallen out of the calyx, carrying with it the oral nerve-ring 

 (Fig. 20, nr). We are led to conclude, therefore, that besides the additional elements in their 

 blood-vascular system, the Crinoids also possess a complicated system of motor-nerves, which is 

 altogether unrepresented in the Eckinozoa. 



The food of the Crinoids is mostly microscopic in character, such as Foraminifera, Infusoria, 

 Entomostraca, and the larvae of the higher Crustacea. They are very gregarious, as are most of the 

 Echinoderms, the Stalked Crinoids living in great forests on certain parts of the sea-bottom, just as 

 they did in previous geological periods. 



During a recent exploration of the Caribbean Sea by the United States Coast Survey, no less 

 than one hundred and twenty-four specimens of Pentacrini were obtained at a single haul of the 

 dredge and its appendages. These must have swept over actual forests of the Sea-lilies, crowded 

 together just as they must have lived in the old Liassic seas. Both in England (as at Lyme 

 Regis) and abroad large slabs of shaly limestone are found containing collections of fossil 

 Pentacrinites, some of them very perfect and remarkable for the great length of their stems. The 

 total length of the stem of one specimen found in Germany, as measured by its broken pieces, was 

 found to be seventy feet, while others with stems fifty feet long are not uncommon. They must have 

 presented a curious sight in their native seas, each with its long stem on which was the crown of 

 arms, not more than two feet across when fully expanded. 



The Crinoids of the Palaeozoic period differ very considerably from those preserved in the 

 Secondary and Tertiary rocks. In many of them the mouth was not on the external surface of the 

 body, for it was covered in by a dome of rigid heavy plates. But there were food-grooves on the arms, 

 just as in the recent Sea-lilies and Feather-stars, and at the circumference of the dome were a number 

 of openings, one for each groove, through which the food particles passed on their way towards the 

 mouth. 



The earliest representative of the more modern type of Crinoid in which the mouth is open to 

 the exterior is the " Lily Encrinite," from the Trias of Germany, a very elegant and well-known 

 species. In an old German book about the natural history of Altenburg, dated 1774, it is recorded 

 that the Emperor of Germany once offered a hundred thalers for a good specimen of this Stone-lily 

 attached to its stem, and free from the matrix in which it had been embedded. 



Little need be said about the Cystoidea and the Blastoidea, two groups which are of the highest 

 Ecological interest, owing to their furnishing numerous connecting links between the Crinoids and the 

 Echinozoa. They have been extinct since the close of the Palaeozoic epoch. They were stalked 

 Echinoderms, like the Crinoids, with food-grooves converging towards a central or excentric mouth, 

 and were provided with respiratory organs, much resembling the interradial pouches of the Ophiurids 

 in their general structure, while it is very doubtful whether their water-vascular system was provided 

 with tentacles. As in the Crinoids, the body-walls were supported by limestone plates, which were 

 arranged very regularly in the Blastoids, but somewhat less so in the Cystids. 



Further information upon the subject of the Echinoderms will be found in the works of Agassiz, 

 W. B. Carpenter. Duncan, E. Forbes, H. Ludwig, Liitken, Lyman, Metschnikoff, J. Miiller, Sars, 

 Selenka, Semper, Sladen, Wyville Thomson, and others. 



P. HERBERT CARPENTER, 



