A RETROSPECT. xi 



Ecliiiiides of the United States in the works published during tlie last twenty years. Oa 

 the other hand, assisted by the activity of my learned friend M. Cotteau, whose name 

 I have had to mention in connection with the Echinitic faunas of almost every region, 

 the fossil Echinides of the Antilles are now very well known. Mr. Guppy had already 

 published nine new species from the Tertiary formations of the Island of Anguilla. M. 

 Cotteau (102) has added as many as twenty-six Eocene and Miocene forms. He has 

 made known the magnificent species of the genus Asterostoma (103), of which we had 

 known only up to the present the single individual type, coming from the Tertiary strata 

 of the Island of Cuba, where it is accompanied with some other species, which will 

 be figured afterwards. 



In South America the Echinitic works within my knowledge are the isolated 

 descriptions of some new species. Philippi (104) has described some from Bolivia; 

 Herr Steinraann (105) has just added two others ; and I have described one from 

 Ecuador (106). 



To this rapid expose of the progress of our knowledge of the fossil Echinides 

 during the last twenty years, it will not be out of place to add a few words on the 

 recent discoveries which have been made among living Echinides in the existing seas. 

 It does not, however, appear necessary to enter into much detail or to do more than 

 mention the published works. The magnificent and excellent work of Alexander 

 Agassiz (107), 'Revision of the Echini,' published between 1872 and 1874, faithfully 

 resumes all the works anterior to it, and, so to speak, fixes our ideas upon the species of 

 Echinides known up to this time in our seas. It will always serve as a point de depart 

 for all future works. The number of distinct species which are there found estab- 

 lished and described amounts to 206. Since then the number has been considerably 

 augmented, but always and almost solely by the recent Expeditions undertaken for the 

 exploration of the bed of the sea, aided by dredges and appropriate machinery placed at 

 the command of the explorers. Most of the new types which have been discovered 

 belong to the most extraordinary forms ; and some of these represent genera found 

 hitherto only in a fossil state, connecting in a very remarkable manner the existing fauna 

 with that of former times. Already in the Dredging Expedition of the " Porcupine," 

 Wyville Thomson had observed in the living state and made known in a complete 

 manner t\ie Asthenoso7na (109), those regular Urchins so curious with a flexible test com- 

 posed of imbricated plates, reminding us of certain Palaeozoic genera and belonging to 

 a family, the EchinothuriDvE, represented up to the present time by some fragments 

 found in the Upper Chalk and a single example of a recent species from an uncertain 

 province. We know actually that it was one of two species all living in depths from 

 10 to 2,750 fathoms, but principally in the greatest depths. The appearance of the first 

 species oi Pourtalesia, dredged by Francois de Pourtales in the latitude of the Antilles, 

 had astonished all the Echinologists. Tins extraordinary genus, bordering on the 

 Holaster and almost on the In/ulaster, approached more particularly the Urchins of the 



