Vi. PREFACE. 



Mr. F. B. Meek. Six plates have been engraved on steel by 

 Mr. J. E. Gravit, and ten more plates are in the engraver's hands. 

 The number of species will probably bp twenty-four, of which 

 Mr. Hall has already given a description in the Report of Progress 

 for the year 1857. 



On the appointment of Mr. E. Billings as Palfeontologist of the 

 Survey, in 1856, his first duty was to effect an arrangement of the 

 Museum. This being accomplished, lie devoted his attention to a 

 third decade. This comprehends all the Gystideae and Star-fishes, 

 as well as all the Entomostraca, of the collection. With the view 

 of obtaining the plates necessary for the illustration of these, Mr. 

 Billings, in the month of February last, carried his fossils to London. 

 Finding that considerable delay was likely to attend the publication 

 of the decade should he illustrate it by engravings on steel, he 

 determined to have recourse to lithograph3^ Although minute 

 detail cannot be so finely given by this mode, nor so large an 

 edition be obtained, it is yet perfectly suitable for all practical 

 purposes. It is occasionally used for the fossils of the British 

 Survey, and very generally for the illustration of the best palseon- 

 tological works on the continent of Europe. The twelve plates 

 which illustrate the third decade are the work of several well-known 

 artists, who have all their respective merits. One of the plates is 

 by Mr. R. C. Bone, two of them by Mr. J. Dinkle, four by Mr. 

 Tuffen West, three by Mr. H. S. Smith, one by Mr. W. Sowerby, 

 and one by Mr. G. West. Of the descriptive part, the Cystideae 

 and Star-fishes are by Mr. E. Billings ; the genus Cyclocystoides by 

 Mr. Salter and Mr. Billings; and the Entomostraca by Mr. T. R. 

 Jones, assistant-secretary of the Geological Society of London, who 

 is considered the best authority on this particular family of animals, 

 and had previously described a large number of the Canadian species. 



While Mr. Billings was attending to the progress of his decade 

 in London, it appeared doubtful which of the three that were in 

 hand would be first ready for publication. He, in consequence, 

 caused to be registered on the plates, as the number of the decade, 

 the figure which indicates the order in which it was commenced. 



