THE LOWER DEVONIAN FISHES OF GEMUNDEN. 737 



generic name being adapted from the name of the district in which Gemiinden is 

 situated, namely, the " Hunsriick" or Dog Bach. 



I am indebted to my friend Professor Jaekel for his good offices in procuring for 

 me the loan of the above described specimen, which is in the collection of the Prussian 

 Geological Survey, Berlin. In accordance with his request, I append an extract from a 

 letter which I received from him shortly after the specimen arrived in Edinburgh. 



" Ueber die Wirbelsaule, die ich Ihnen sandte, ist meines Wissens nichts gedruckt 

 worden. Ich habe einen Yortrag darliber gehalten in dem ich auf Grund dieses Stuckes 

 betonte, dass die iibliche Vorstellung einer langsamen Heranbildung der Wirbelsaule 

 innerhalb der Fische irrig sei. Die von verschiedenen Typen des Devon vorliegenden 

 Wirbelsaulen erfuhren bei den Fischen zunachst eine Keduction der Verknbcherung, um 

 sich dann innerhalb der Fische neu auszubilden. Die vorliegende dem untersten Devon 

 angehorende Wirbelsaule beweist, dass vor den bekannten Ganoiden, Haien, und andern 

 Fischen, Vertebraten mit echter Wirbelsaule existirten. Diese Thatsache war mir 

 deshalb bedeutungsvoll, weil sie die Wahrscheinlichkeit erhoht, dass jene altesten Fische 

 von terrestrischen Tetrapoden abstammen. Ich wiirde Ihnen sehr dankbar sein wenn 

 Sie das in Hirer Arbeit als meine Ansicht dariiber benutzten." [Letter dated SOth 

 January 1900.) 



The scope of this paper being, as I have explained on a previous page, purely de- 

 scriptive, I cannot enter into a discussion of the point raised in the above extract. I am 

 however obliged to confess that, though I am sorry to disagree with Professor Jaekel, 

 I cannot as yet see my way to adopting the view that fishes are descended from 

 terrestrial tetrapod animals, which have found in the water a new direction for their 

 evolution. 



EXPLANATION OF THE PLATES. 



[All the figures in the following Plates have been reproduced from photographs taken from the specimens themselves, 

 except in the case of fig. 1 PI. I. and fig. 1 PI. V., in which the photographs were, for convenience' sake, taken from plaster casts. 

 In both of these cases, however, the original specimens were carefully studied.] 



Plate I. 



Fig. 1. A nearly entire specimen of Drepanaspis Gemundenensis, dorsal view, the extreme front and a 

 part of the right side of the carapace being, however, defective, as is also a portion of the circumference in the 

 anterior part of the left side and the posterior external angle of the left dorso-lateral plate. The scales of 

 the tail are obscured by a covering of pyrites as far as the caudal fin, which is well preserved. The present 

 illustration has been taken from an excellent plaster cast of the original specimen which is contained in the 

 collection of the Prussian Geological Survey in Berlin. Reduced by one-fifth. 



