522 SCIENCE PROGRESS 



standpoint, and contains much information and many sugges- 

 tions as to the habits, phylogeny, and migrations of these 

 Palaeozoic fishes. An interesting generalisation, based upon 

 examples from numerous groups, is that those types of fishes 

 which show no tendency to progressive evolution undergo a 

 kind of degenerative development so as to assume a more or 

 less distinctly eel-like form of body. This is true among the 

 acanthodian sharks, which declined towards the close of the 

 Palaeozoic epoch, dying out Iwith the Permian. Their fins, 

 being essentially skin-structures, were incapable of strengthen- 

 ing by bony rods, after the fashion obtaining in other con- 

 temporary and competing groups. Hence these fishes, as they 

 became worsted in the struggle for existence, changed their 

 habits and their physical structure. Devonian species, for 

 example, with the graceful fusiform proportions of swift 

 swimmers, became replaced in the Carboniferous by over- 

 grown, unwieldy creatures like Gyracanthodes, which were 

 evidently grovellers in the slimy mud of land-locked seas and 

 estuaries ; while the expiring Permian forms exhibit a distinct 

 approximation to the eel-like type of body. 



Passing southward of the isthmus of Panama, fish-remains 

 from the Cretaceous of Bahia form the subject of a paper by 

 Dr. A. Smith Woodward in The Quarterly Journal of the 

 Geological Society (vol. lxiii. p. 131). These indicate a curious 

 mixture of Wealden and middle or upper Cretaceous types ; 

 Lepidotas mawsoni being, for instance, near akin to the well- 

 known L. mantclli of the English Wealden, while Megalurus 

 mawsoni appears to be a Jurassic rather than a Cretaceous 

 form of amioid fish. On the other hand, the freshwater 

 herring Diplomystus longicostatus is a member of a genus 

 common in the upper Cretaceous of the Lebanon and the 

 lower Tertiaries of Europe and North America. The new 

 genus and species Mawsonia gigas, a member of the ccelacanth 

 ganoids, may be either Jurassic or Cretaceous, although more 

 probably the latter. 



The same author has contributed to The Geological Magazine 

 (decade 5, vol. iv. p. 193) an account of the fossil fish-fauna 

 of Pernambuco, in which the new species Rhinoptera prisca is 

 described. 



From the Lahontan beds of Nevada have been obtained 

 remains of a stickleback, which is regarded by Mr. O. P. Hay 



