;i4 



BIBLIOGRAPHICAL NOTICE. 



Thesaurus Siluricus. The Flora and Fauna of the Silurian Period. 

 By J. J. Bigsby, M.D., F.G.S., &c. 4to, pp. i-liv & pp. 1-214. 

 London : Van Voorst, 1868. 

 Dean Contbeare's apothegm, " The boldest and happiest generaliza- 

 tions must depend on details," is the author's motto ; and his book 

 is full of details, with a short Introduction showing what facts and 

 inferences may be derived therefrom, and how they are to be worked 

 out. It is a praiseworthy and elaborate attempt to collect and 

 arrange all that is known of the creatures that existed in the far- 

 back period termed " Silurian " by geologists, and to treat of them 

 as a fauna and a flora, with their regions, provinces, and habitats, 

 their incomings and migrations, their persistency or evanescence, 

 and their relationship as predecessors, if not as ancestors, to such as 

 live and flourish at the present day. 



The body of the work consists of a systematic catalogue of the 

 known Silurian fossils, arranged in natural-history order, as far as 

 existing circumstances permit, together with the authorities for 

 genus and species (the former with dates), and indications of the 

 formations in Avhich the species occurs, and the country in which it 

 is found. The great natural groups adopted are Plantse (p. 1), 

 Amorphozoa (p. 3), Actinozoa (p. 6), Crinoidea (p. 18), Cystidea 

 (p. 24), Asteridea (p. 27), Annelida (p. 29), Trilobita (p. 33), Phyl- 

 lopoda and Ostracoda (p. 72§), Polyzoa (p. 78), Brachiopoda (p. 88), 

 Monomyaria (p. 126), Diniyaria (p. 131), Pteropoda and Heteropoda 

 (p. 143), Gasteropoda (p. 150), Cephalopoda (p. 170), and Pisces 

 (p. 192). An Appendix of Addenda, Errata, List of Authors, and 

 Index of Genera completes the work, which, however, has been 

 supplemented with an additional fly-leaf of corrigenda , chiefly re- 

 lating to double insertions, both old names and synonyms having 

 been catalogued in many instances ; but the correction of these and 

 of numerous other mistakes of copying, misplacement, and omission 

 really makes but a small percentage of difference in tbe estimated 

 totality of known Silurian life ; and the author's figures may be taken 

 for fairly approximate statistics whereon to found the biological in- 

 ferences and philosophical conclusions which in part he produces, 

 and in large part he wishes others to work out. 



Dr. Bigsby supplies in the introductory " Facts and Observations" 

 some highly suggestive essays, pregnant with useful truths. 1st. 

 On the influence of Locality on the nature and amount of life, 

 p. xxxiv, he observes that, as " every tolerably large space of sea- 

 bottom has its own conditions and its own fauna," and as " the 

 physical state of land and sea was and is as local as the population," 

 every considerable Silurian region contains much that is peculiar, 

 generic alliances being the main links between the creatures of dif- 

 ferent Silurian areas. " The maximum of life is usually local, 

 meaning by that expression the largest combination of abundance, 



