336 



Recherclws sur les Poissons Fossiles, 



are not sufficient in thickness to relieve the intervals 

 from space to space of one side/ 1 ) as we see also in 

 some species of Tellines. It is always at the posterior 

 border of scales that we observe on the sides of the 

 leaves of growth, those points to which, according to their 

 form we have given the names of cilice^ denticules, spines^ 

 and also of ridges ; and as it is this part of the scale which 

 is visible on the surface of the fish ; it is also to this dis- 

 position of the scales that the asperities of the skin in the 

 Perches, the Chetodons, and the Pleuronectes, is owing ; 

 in these the inequalities in question are most prominent. It 

 is no objection whatever to this, that their anterior border 

 may not be more or less lobed, as it would be all the same if 

 it were perfectly smooth. 



When the scales have acquired a certain development, 

 and their external surface has been consequently for a long 

 time in contact with the enveloping medium, it frequently 

 happens that the first formed filaments desiccate, harden, and 

 are detached from the middle of the scale, under the form 

 of little irregular palettes or spangles, which render the cen- 

 tral parts very unequal, and give to them quite a different 

 aspect from that which belonged to them when the fish was 

 smaller. Nothing can illustrate these changes better, than 

 the scales in old Carps when compared with young indi- 

 viduals. 



There is yet one peculiarity in certain scales which tends 

 to render their surface unequal ; namely, a number of fur- 

 rows which extend in different directions from the centre 

 of growth, or some other part of the scale to the border/ 2 ) 

 which they do not however always reach. (3) In some species 



0) Selecta genera, Tab. F. Mesoprion, Corona, Pachyurus. 

 12) Selecta genera, Tab. C. Erythrimus unitceniatus, Tab. F. Batrachus 

 punctatus, Lobotes ocellatus et Mesoprion. 

 (;,) ) Clupanodon ansens, Clialcens angulatus. 



