Fauna of the Carihhean Sea &c. 313 



zoology to make exceeds any thing that could have been hoped 

 for ; and almost every day new facts are added to those already 

 known. Those seas which had been best explored, and with 

 regard to which naturalists thought there was nothing more 

 to be learnt, have furnished unexpected discoveries when those 

 zones which the fishermen do not usually reach came to be 

 investigated. 



I have already had occasion to call the attention of the 

 Academy to the results obtained last summer oh board the 

 ' Travailleur ' off the northern coast of S]iain ; and I dwelt 

 especially upon the difference that exists between the animal 

 population of the great depths and that of the surface or of 

 the shores. "When we compare their representatives it is as 

 though we had before us two distinct faunas belonging neither 

 to the same time nor to the same climate. The importance 

 of this fact cannot escape any one ; and geologists, in the 

 determination of the age of a formation, must take it seriously 

 into account. In fact, at the present day, in the same seas, 

 there are in course of formation deposits, as to the contempo- 

 raneity of which there can be no doubt, and which contain the 

 remains of perfectly dissimilar creatures. The animals of the 

 littoral deposits belong to types of higher organization 5 those 

 of the deeper deposits have a more ancient character : some of 

 the latter present incontestable affinities with the fossils of 

 the Secondary epoch ; others resemble the larval condition of 

 certain existing species. 



The investigations which I have lately made of the Crus- 

 tacea of the Caribbean Sea and Gulf of Mexico have furnished 

 interesting results ; and I think it worth while to say a few 

 words about them. The materials I have had at my disposal 

 were abundant and varied ; for Mr. Alexander Agassiz had the 

 kindness to send me for determination all the Crustacea col- 

 lected by the expeditions of the U. S. navy during the years 

 1877, 1878, and 1879. A special ship, the ' Blake,' was 

 fitted out for the performance of deep dredgings ; and the 

 harvests collected by her have proved most fruitful. I have 

 now completed the examination of all the Brachyurous Deca- 

 pods, of the Anomura, and the Cuirassed Macrura ; I have 

 described them in the Bulletin of the Museum of Comparative 

 Zoology at Harvard College"^; and now, treating the question 

 from another point of view, 1 shall confine myself here to the 

 indication of the general results at which I have arrived. 



The number of species collected is much greater than would 

 have been supposed from what was known of this part of the 

 * "Etudes piulimiiiaires sur les Crustaces," par A.Milne-Edwards 

 ( 1'' partie), Jkill. Mus. Oonip. Zool. Harv. Coll. tome viii. uo. 1. 



Ann. & Mag. N. Hist. Ser. 5. Vol. vii. 23 



