SEVENTH JURASSIC PERIOD. 



Of Crustacea 31 were created, all of which became extinct at 

 the close of the period, so that the total number of generic forms 

 ascertained to have lived is 213, of which 82 were created, and 

 131 revived, exclusive of other Annulata, the existence of which 

 has been determined but their numbers unascertained. 



372. This period is signalised by the first appearance of insects, 

 of the orders Hemiptera (bugs, water- scorpions, plant-lice), 

 Hymenoptera (bees, ants), and Lepidoptera (butterflies, moths), 

 and of Isopodous Crustacea, and the prevalence of testaceous spon- 

 gearia, pterodactyles, pycnodide fishes, and decapod Crustacea. 



373. Of Mollusca and Annulata of this period, 729 species 

 have been catalogued, and 



the total number of species 

 of all classes could not have 

 amounted to less than 800. 

 In fig. 166 is shown a 

 specimen of the insects of 

 this period, and in fig. 167, 

 one of the Annelids. 



374. The seas retained 

 their former limits ; those 

 of the Parisian and Pyre- 

 nean basins, however, re 

 tiring as before stated, so 

 as to leave a new band 

 of surrounding coast un- 

 covered. They extended 

 over the same parts of 

 Europe, and were continu- 

 ous on the one side to Asia 

 Minor, and on the other 

 into Russia, as is proved 

 by the prevalence of the 



J Fig. 167. Serpula flagellum. 



same marine species in the 



strata. The Breton and Vosgian Straits were still replaced by 

 isthmuses. 



375. Adolphe Brongniart has enumerated a considerable as- 

 semblage of marine plants of this period, consisting chiefly of 

 Cryptogamous Algse. 



376. The continents were not less animated than the seas. 

 Besides several orders of insects, and the generic reptile forms of 

 the preceding periods, 10 new reptile genera were called into 

 existence, including the Gnathosaurus, Pleurosaurus, Greosaurus, 

 and Spondylosaurus, which, as well as new species of ptero- 

 dactyles, abounded. M. Brongniart has also given a list of the 



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