OP THE SKULL IN SHAKES AND SKATES. 191 



Albert G&nther. "Description of the Ceratodus, a Genus of Ganoid Fishes recently discovered 

 in Rivers of Queensland^ Australia." Phil. Trans. 1871, part ii. pp. 511-571, pi. 30— 1'2. 



Carl Gegenbaur. ' Untersuchungeu zur Vergleiehenden Anatomic der Wirbelthiere ' (pait 3. 

 Selachians). Leipzig, 1873. 



Then follow in natural order, the writer's own papers in the ' Philosophical Trans- 

 actions ' on the structure and development of the skull in various types. The present 

 paper is one of the same kind, but especially intermediate between M. Gegenbaur's 

 splendid work and the invaluable researches now to be noticed. 



F. M. Balfour — 



1. " A Preliminary Account of the Development of the Elasmobranch Fishes." Quart. Jouru. of 



Micr. Sc. Oct. 1874. 

 3. "The Development of Elasmobranch Fishes." Journ. of Anat. & Phys. vol. x. pp. 517-570, 

 pi. 31-26. 



3. "The Development of Elasmobranch Fishes." Ibid. pp. 677-688, pi. 39. 



4. 'A Comparison of the Early Stages in the Development of Vertebrates : Studies from the Phy- 



siological Laboratory in the University of Cambridge.' Part ii. 1876, pp. 1-30, pi. I. 



Although out of order, I must mention two important papers recently sent me by 

 the author. 



Burt G. Wilder. 



1. "Notes on the North-American Ganoids Amia, Lepidosteus , Acipenser, and Polyodon." Proc. 



Am. Assoc, for Adv. of Sc. : Detroit Meeting, Aug. 1875. Salem, Mass., 1876, pp. 151-194, 

 pi. 1-3. 



2. " Note on the Development and Homologies of the Anterior Brain-maas of Sharks and Skates." 



Am. Journ. of Sc. & Arts, vol. xii. Aug. 1876'. 



I mention these last papers because of the necessity of studying the nervous and 

 skeletal systems together, and also because of the intimate relation of the Selachians 

 with the Ganoids. 



In the following description allusion will be made to the condition of the stages of 

 the skull in other types, especially in the Ichthyopsida. 



But the intimate relation of the skull of the Amphibia with that of the Selachians 

 is best seen in the outlying forms of the latter group, namely Cesfracion, Notidanits 

 {Ileptanclius, and Hexcmchiis), as these come nearest to the Chimseroids on one hand, 

 and to the ferval Batrachia and Urodela on the other. 



Professor Huxley's paper on Menohranchus, a Perennibranchiate Urodele, has been 

 of the utmost service to me ; and by the time the present communication is published, 

 I hope to have also in print my second paper on the Batrachian skull, and my first on 

 that of the Urodeles. These, in addition to remarks on the growth and changes of the 



' Several fresh papers by my friends Balfour and Wilder have reached me since the above list was written. 



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