x.] PERSISTENT TYPES OF LIFE 221 



PalcBOoyclus less highly organized or more embryonic 

 than the modern Fungia, or the Liassic Aporosa than 

 the existing members of the same families ? 



The Mollusca. — In what sense is the living Wold- 

 lieimia less embryonic, or more specialized, than the 

 palaeozoic Spirifer ; or the existing Rliynchonellco, Cra- 

 nio?, Discince, Lingulce, than the Silurian species of the 

 same genera ? In what sense can Loligo or Spirilla 

 be said to be more specialized, or less embryonic, than 

 Belemnites ; or the modern species of Lamellibranch and 

 Gasteropod genera, than the Silurian species of the same 

 genera ? 



The Annulosa. — The Carboniferous Insecta and Arach- 

 nicla are neither less specialized, nor more embryonic, 

 than those that now live, nor are the Liassic Cirripedia 

 and Macrura ; while several of the Brachyura, which 

 appear in the Chalk, belong to existing genera ; and 

 none exhibit either an intermediate, or an embryonic, 

 character. 



The Veiltebrata. — Anions fishes I have referred to 

 the Ccelacanthini (comprising the genera Caelacanthus, 

 Holophagus, Undina, and Macropomci) as affording an 

 example of a persistent type ; and it is most remarkable 

 to note the smallness of the differences between any of 

 these fishes (affecting at ' most the proportions of the 

 body and fins, and the character and sculpture of the 

 scales), notwithstanding their enormous range in time 

 In all the essentials of its very peculiar structure, the 

 Macropoma of the Chalk is identical with the Cazlacan- 

 thus of the Coal. Look at the genus Lepidotus, again, 

 persisting without a modification of importance from the 

 Liassic to the Eocene formations inclusive. 



Or among the Teleostei — in what respect is the Bcryx 

 of the Chalk more embryonic, or less differentiated, than 

 Berijx lineatus of King George's Sound \ 



