346 



Nachdruck verboten. 



Note on the Basi branchial Skeleton of Echinorhinus spinosus. 



By Dr. W. G. Ridewood. 

 With one Figure. 



Od account, probably, of the rarity of its occurrence, the Spinous 

 Shark (Echinorhinus spinosus) has received but little attention 

 from anatomists. It is highly desirable, therefore, that any feature of 

 interest in its anatomy should be placed on record, in view of the 

 difficulty that morphologists must experience of conducting personally 

 an autopsy upon it. 



A specimen of this shark, seven feet long, was caught in the 

 Bay of Biscay on December 20th 1898, and was brought to the London 

 fish-market. It was purchased, and presented to the Natural History 

 Museum by Mr. C. H. Akkoyd, and was dispatched to a taxidermist 

 to be stuffed. I applied for permission to examine the skinned car- 

 case, which was readily granted, and I retained for more minute in- 

 vestigation the vertebral column and the branchial skeleton. The fins 

 and skull had been removed with the skin, and the alimentary viscera 

 had been excised on board the boat. An account of the vertebrae of 

 Echinorhinus has already been given by Hasse in his great work 

 on the vertebrae of Elasmobrauchs 1 ), but the branchial skeleton has 

 been neither figured nor described. 



The Echinorhinus is usually associated 2 ) with Laemargus 

 and Scymnus, and the spiny-finned forms Acanthias and Spin ax; 

 but its basibranchial skeleton differs from that of these four genera 

 in numerous respects. 



In all Elasmobranchs the hindermost cartilage of the mid-ventral 

 series is a broad plate situated below the front of the pericardium. 

 In the more specialised forms this constitutes the whole of the basi- 

 branchial skeleton, but in the lower forms there occur in front of it 

 one or more median cartilages, which can usually be identified as apper- 

 taining to the second, third or fourth branchial arches. In S p i n a x 3 ), 



1) Das natürliche System der Elasmobranchier. Jena, 1879 — 1885. 



2) Müller and Henle, Systematische Beschreibung der Plagio- 

 stomen. Berlin, 1841. — Günther, British Museum Catalogue of Fishes, 

 Vol. 8, 1870. — Hasse, loc. cit. 



3) Gegenbaur, Das Kopfskelet der Selachier, Leipzig 1872, Taf. 

 XVIH, Fig. 6. 



