( 171 ) 



Observations upon the Fossil Polypi of the Genus Eschara, 

 (Millepora, Lin.) By M. H. MILNE EDWARDS. 



AT the meeting of the Academic dcs Sciences of Paris, on 

 Monday the 21st of November last, M. Milne Edward read an 

 interesting paper on this subject, of which the following is the 

 substance. 



The stony, or rather the bony, texture of the external tunic 

 of the Eschara affords very favourable conditions for the pre- 

 servation of the remains of these polypi in the slimy deposits 

 which have successively invaded their abode, so that, in spite 

 of their extreme delicacy, they are frequently encountered in a 

 fossil state ; and at the present moment the number of extinct 

 species, whose existence is regarded as established, greatly ex- 

 ceeds that of the recent species detected by zoologists in our 

 present seas. The examination of these fossils has never- 

 theless been for long neglected, and the list of the authors 

 who have treated of them is very short. M. Desmarest has di- 

 rected the attention of naturalists to several species ; Faujas 

 de Saint Fond and Lamouroux have also discovered some ; but 

 it is chiefly in the work of M. Goldfuss that we must look for 

 that precise and minute information which will be truly useful. 



At the same time, it must be confessed that the study of these 

 polypidoms is attended with considerable difficulty, inasmuch asit 

 requires a minute examination of the conformation of the almost 

 microscopic cells of which they are formed ; and in order that the 

 drawings which are taken may be satisfactory, it is necessary that 

 the objects should be magnified at least twenty times, and that the 

 relative sizes of the different parts should be maintained. But that 

 which principally diminishes the value of the labour which has 

 previously been bestowed on this department of natural history, 

 is the ignorance which prevailed concerning the modifications of 

 the forms which were induced by age on the polypus in each 

 cell ; for, in the want of the knowledge of this fact, inquirers 

 were naturally led to be content with the examination of a few 

 well-preserved cellules in each polypidom, and thus proceeding, 

 were liable, on the one hand, to multiply species without suffi- 

 cient ground, and, on the other, to confound species which were 



