348 Miscellaneous. 



number of Cidaridae is very considerable, 24 French species being 

 recorded by M. Cotteau. Of these, 19 are peculiar to the stage ; 

 1, as already stated, is of older date ; 4 pass into the next stage ; 

 and one of these {Rhabdocidaris copeoides) extends up through the 

 two subsequent stages. 



In tbe Eathonian (Great Oolite) we have 20 species, 13 of which 

 are peculiar, 4 had previously appeared, and 5 extend up into 

 higher deposits ; 3 of them, however, do not occur in the next 

 following stage, but only in the one above it. The Callovian con- 

 tains only 6 species, 4 of which are peculiar, and 2 extend up into 

 the succeeding stage, 1 of them belonging also to that below. The 

 Oxfordian, including therein the zone of Ammonites tenuUobatus, 

 has 24 species, 4 of which had already made their appearance in 

 the Bathonian, while 7 others extend up into the Corallian, and 

 one of them even into the Kimmeridgian stage. 



The family attains its maximum in the Corallian stage, from 

 which M. Cotteau records 38 species, 29 of which are peculiar to 

 this series of deposits. Seven species, as already stated, come up 

 from the Oxfordian, while 3 recur in the next stage, the Kim- 

 meridgian, which, however, has altogether only 9 species. The 

 Portiandian has only a single peculiar species. 



M. Cotteau sums up his results as follows : — " Of 121 species of 

 Cidaridae which were developed in France during the period of the 

 Jurassic formation, 104 are, as at present known, peculiar to the 

 stages in which they are found, and only 17 occur in more than one 



" The three genera Cidaris, Rhabdocidaris, and Diplocidaris have 

 each a different origin and destiny. 



"The genus Cidaris, including the greatest number of species, is 

 of all genera of Echinida the one that has persisted longest. It 

 makes its appearance in the deposits of the Carboniferous forma- 

 tion ; from this period it multiplies its species in all the stages of 

 the Jurassic, Cretaceous, and Tertiary formations ; and at the 

 present day it still possesses representatives in most of our seas. 

 Notwithstanding this long duration, from its first appearance to the 

 present epoch it has undergone in its general characters only un- 

 important modifications, which often render it difficult to distin- 

 guish the species. 



"The genera Rhabdocidaris and Diphcidaris have been separated 

 from Cidaris. The former began to appear in the Liassic stage, and 

 attains its maximum of development during the Jurassic epoch ; it 

 likewise exists in the Cretaceous and Tertiary formations and at the 

 present epoch, but is much rarer. The second genus, Diplocidaris, 

 is peculiar to the Jurassic formation, and indeed does not exist even 

 in its last stages. 



" Over and above the 121 species of Jurassic Cidaridae described 

 and figured in the ' Pale'ontologie Franchise,' the genus Cidaris has 

 furnished us with 47 species, 44 of which are foreign to our country ; 

 the genus Rhabdocidaris with 10, and Diplocidaris with 3 species 

 foreign to France ; which raises the number of species of Jurassic 

 Cidaridae that we know at present to 181." — Bidl. Soc. Geol. France, 

 3me S e r# torn. vii. p. 246. 



