516 Notices of Memoirs— Dr. R. B. Traquair's Address. 

 IsTOTICES OiF iycE2vnoiK-s - 



Bbitish Association for the Advancement of Science, 

 Bradford, 1900. 



Address to the Zoological Section. By Eamsay H. Traquair,. 



M.D., LL.D., F.E.S., President of the Section. (Slightly abridged.) 



{Concluded from the October Number, p. 470. )i 



COMING- now to say a word regarding the Elasmobranchii, it is 

 plain from the fin-spines found in Upper Silurian rocks that they 

 are of very ancient origin, and that if we only knew them properly 

 they would have a wonderful tale of evolution to tell. But their 

 internal skeleton is from its nature not calculated for preservation, 

 and for the most part we only know those creatures from scattered 

 teeth, fin-spines, and shagreen, specimens showing either external 

 configuration or internal structure being rare, especially in Palfeozoic 

 strata. But from what we do know, there is no doubt that the 

 ancient sharks were less specialized than those of the present day, 

 and that the recent Notidanids still preserve peculiarities which 

 were common in the Selachii of past ages. 



If we ask whether the fossil sharks throw any light on the 

 disputed origin of the paired limbs, whether from the specialization 

 of right and left lateral folds, or whether that type of limb called 

 ' archipterygium ' by Gegenbaur, consisting of a central jointed axis 

 with pre- and post-axial radial cartilage attached, was the original 

 form, I fear we get no very definite answer from Elasmobranch 

 palaeontology. The paired fins of the Upper Devonian shark, 

 Cladoselaclie, as described by Bashford Dean, Smith Woodward, and 

 others, seem to favour the lateral fold theory, and Cope pointed to 

 the right and left series of small intermediate spines which in some 

 Lower Devonian Acanthodei {Parexus and Climatius) extend between 

 the pectorals and ventrals as evidence of a former continuous lateral 

 fin. So also, if 1 am right in looking on the lateral flaps of the 

 Coelolepidge as fins, the evidence of these ancient Ostracodermi would 

 be in the same direction. 



But, on the other hand, we have the remarkable group of 

 Pleuracanthidas, extending from the Lower Permian back to the 

 Upper Devonian, in which the paired fins are represented by an 

 ' archipterygium ' which in the pectoral at least is biserial. 



From this biserial ' archipterygium ' in the Pleuracanthida, 

 Professor A. Fritsch, ten years ago,- derived the tribasal arrange- 

 ment of modern sharks, much according to the Gegenbaurian method, 

 effecting, however, a compromise with the lateral fold theory by 

 assuming that the Pleuracanth form originated from one, consisting 

 of simple parallel rods, like that described in Cladoselaclie. 



1 The reader is requested to note the following errata in the part of this Address 

 published in our last number, namely, at p. 465, line 30, for "Under" read 

 " IJnless," and in line 31 delete the semicolon after "pectorals." 



^ "Fauna der Gaskohle uud der Kalksteine der Permformation Bohmens," 

 vol. iii, pt. 1 (Prague, 1890), pp. 44-45. 



