xii BRITISH FOSSIL ECHINODERMATA. 



White Chalk. We have lately discovered that there are several species, most of them 

 bizarres forms ; and the Expedition of the " Cliallenger " has made known many new 

 genera, which are connected with it, so that now this species, known at first by a single 

 example, has become the 2^oint de depart, a few years after its discovery, of a family 

 which appears to be truly limited to great depths. These two examples will suffice 

 perhaps to make us appreciate the development of our knowledge of the Echinides of 

 the actual seas during the last eight years. 



I do not intend to enlarge here upon the new species and the new genera which have 

 been successively brought to light by the dredging expeditions of the " Porcupine," of 

 the "Easier" (110), of the " Josephine," of the "Blake" (HI), of the " Challenger" 

 (112). This last, which perhaps may be considered the most fruitful, has brought to our 

 knowledge no less than forty-four new species and sixteen new genera. We are able to 

 estimate roundly at 300 the number of the species which we know in our actual 

 seas, and it is not only the discovery of new types which we owe to these expeditions, 

 so rich in results of all kinds, but numerous and valuable indications and informa- 

 tion on the geographical distribution of species, and on their vast bathymetrical limits, 

 which are of the greatest utility in explaining certain facts relative to the distribution 

 of fossil species, a subject upon which, perhaps, we may have experienced embarrassment. 

 Now that we know that the Sjxifangus Basin is found from the Hebrides to the Cape of 

 Good Hope, that the Brissojjsis lyrifera and the Schizaster fragUis are met with both in 

 the seas of Norway and in the south of the Indian Ocean, and that certain species of 

 Cidaris descend from the shore to 2000 fathoms, and that a Phormosoma descends from 

 200 to 2700 fathoms, many facts relating to fossil Echinides will perhaps be able to find 

 an interpretation. 



This is not the place to recapitulate the progress of the state of our knowledge upon 

 the Morphology, the Anatomy, and the Embryogeny of the Echinides ; moreover, I am 

 not competent to imdertake the work. 



I desire only to mention a remarkable w^ork by M. Loven (113), ' fitudes 

 sur les Echinides,' accompanied by fifty-three excellent plates which contain very 

 curious and most interesting researches on the structure of the solid skeleton of Urchins, 

 and on the different points in their organisation. This useful work ought to be studied 

 by all those who wish to make the Echinides the object of serious research. 



My task is now brought to a termination. I hope that those who, in the next 

 twenty years, undertake a similar work will be able to register as many new facts, as 

 many new discoveries, and as much progress of all kinds in the study of this very 

 interesting group of animals, of which T have endeavoured to give a resume in the fol- 

 lowing summary Table, which is probably less complete than I wished it to be. 



