ZOOLOGY. 371 



developmeut which bave resulted in the completely ossified and highly 

 organized Siluroids now existing." 



xWe give these results of Mr. Davis' investigation on account of the 

 importance of the question involved, but it seems best to add that there 

 can be no close relationship between the Teleosts and the Selachians, 

 and that the question as to the relationship of the palaeozoic fishes can 

 only be ascertained after the examination of specimens in a far more 

 satisfactory condition than any that have yet been found. 



THE PLATYSOMIDS AND PAL^ONISCIDS. 



Tu^o of the most frequently occurring groups of fishes occurring in the 

 l)aleozoic formation are the Pal aeon isci dee and the Platysomidae. The 

 affinities of these types have been but little understood heretofore, and 

 Dr. R. H. Traquair has therefore been led to a re-examination of the 

 subject.* He has reached the following conclusions: 



" 1. That the Platysomidae are specialized forms, which have, if the 

 doctrine of descent be true, been derived from the Palaeoniscidae. Their 

 structure presents us simply with a modification of the Palieoniscoid 

 type; and wherever the Paheouiscida) are placed in the system, thither 

 the Platysomidee must follow. 



"2. The resemblances between the Platysomida; and the Dapediidie 

 and Pycnodontida3 are mere resemblances of analogy and not of real 

 affinity. The Dapediidae are related not to the Palseoniscidaj or Platy- 

 somida?, but to the other semiheterocercal Ganoids of the Jurassic era 

 (Lepidotus, &c.) ; and the Pycnodonts are higly specialized forms, whose 

 general affinities point in the same direction." 



Professor Traquair concludes that the Palaeoniscidiie and Platysomidie 

 belong to the "Acipenseroid sub-order of Ganoids." 



The characters ascertained to distinguish the Platysomidaj and Pal- 

 jeoniscidae scarcely appear to warrant the conclusions of Professor Tra- 

 quair. Professor Cope, indeed, has been led by the consideration of 

 Professor Traquair's studies to a very difl'erent result, and one approx- 

 imating, apparently, more to nature. Cope t has proposed to differentiate 

 the forms in question as representatives of "a distinct group of the same 

 rank as those [he has] called orders," and given to it the name Lysopteri. 

 They are defined as "actinopterous fishes, with the median fin-rays not 

 joined to the interhaemal and iuterneural bones, and not coinciding with 

 them in number] and without suboperculum." 



ON THE SEXES OF THE EELS.f 



As is generally known, the subject of the reproduction of the eels was 



* Traquair (Ramsay H.)- The PlatysomidjB. Ann. Mag. Nat. Hist., (5), vol. vi, pp. 

 97, 98. On the Structure and Affinities of tlie Platysomidie. Trans. lioij. Soc. Edin- 

 burgh, vol. xxix, pp. 343-391, pi. 3-6. 



t Cope (E. D.). Traquair on Platysomidai. Am. Nat., vol. xiv, pp. 439, 440. 



t Cattle (S. Th.). Ueber die Geuitalien der uiiinulicheu Aale und ihre sexual Untei-- 

 Bcheide. Zool. Anz., vol. iii, pp. 275-279. (On tlio Genitalia of male Eels and their 

 sexual characters. Proc. U. S Nat. Mus., vol. iii, pp. 280-284.) 



