178 Scientific Intelligence — Zoology. 



species embraced are not less than eighty-eight in number, of which 

 only half a dozen have been described. It is the opinion of Professor 

 Hall that all the silurian formations of New York, previous to the be- 

 ginning of the geological survey, did not afford more than four or five. 

 Now, about sixty species have been ascertained. Professor Hall men- 

 tioned the fact, that all the crinoids of the lower silurian rocks, with 

 the exception of one species, have five pelvic plates, and wo never find 

 one with three, or any other number of these plates, before we reach 

 the highest deposits. In Tennessee, the crinoids are so abundant, 

 that Professor T roost states that he had been able to collect some 

 300 or 400 good specimens of seven or eight different species in a 

 single morning. In relation to the abundance of these fossils in the 

 United States, Professor Agassiz remarked, that it is not, perhaps, 

 sufficiently appreciated of what importance, and of what immense 

 value the study of these fossil crinoids may be for the progress of 

 palaeontology. American students should be proud of these mate- 

 rials, by which they will be able to throw so much light upon these 

 almost extinct families by their personal investigations, which will 

 not only render them independent of the palseontologist from abroad 

 for information with regard to the succession of types, and the full 

 illustration of these structures, but really afford correct standards for 

 comparison. It is the more desirable that all these fossils should bo 

 made known, as the family of crinoids is so reduced in our days 

 that we can form no idea of the living animals of that group, of their 

 diversity of form, modification of character, and peculiarity of posi- 

 tion, from the living type only. He doubted whether the number 

 of crinoid heads of all species found in Europe, now existing in the 

 Museums of Europe, is one-third the number of those which have 

 been found by a single gentleman in Tennessee in one morning. 

 Now, with such materials, consider what precise and what minute 

 investigations could be made. And if these facts could be once fully 

 ascertained and well illustrated, there is no doubt that the series of 

 crinoids, and their succession in former ages, will be established from 

 American standards, and will no longer rest upon the European evi- 

 dence, which has often been derived from the examination of small 

 fragments of those ancient fossils, found in unconnected basins for 

 the most part, so that their geological succession could be ascertained 

 only with great doubt and difficulty. In conclusion, Professor 

 Agassiz would venture to say, that geologists who have had any oppor- 

 tunity to compare the position of the ancient rocks on this continent 

 of North America with the corresponding deposits of Europe, would 

 agree with him in saying that the geology proper, the stratography 

 of North America, will afford the same precise and well authenti- 

 cated standards for the appreciation of the order of succession of rocks, 

 as fossils will for the order of succession of living beings. — Ameri' 

 can Annual of Scientific Discovery ^ p 282. 



mal on the shores during the palaeozoic period. Thirty-one genera, sixteen of 

 which are considered by Professor Troost as new, are enumerated. 



