A REVIEW OF THE ELASMOBRANCHIATE FISHES OF 



JAPAN. 



B}^ David Starr Jordan and Henry W. Fo^vler, 



Of the Leland i^Uwford Junior University. 



In the present paper is given a record of the species of Elasmobran- 

 chiate fishes, sharks, rays, and chiman-as, known to inhabit the waters 

 of Japan. It is based on the collections made l)y Messrs. Jordan and 

 Snyder durino- the summer of 1900, and on the material contained in 

 the Japanese museums and in the United States National Museum, 

 some of which were collected by the U. S. Fish Commission Steamer 

 Alhafrfws. The accompanying figures are chiefly ])y Mr. William 

 Sackston Atkinson. 



Subclass SELACHII. 



This includes among recent fishes the sharks and the rays, marine 

 fishes mostly of large size, abounding in all seas. 



We begin the group with the archaic type, the order or suborder 

 Notidani, proceeding thence from the more generalized sharks to the 

 specialized skates. The true sharks form an idmost perfect gradation 

 into the skates, l)ut there are no forms extant which connect the Noti- 

 dani with modern sharks. 



(of'Aarjos-, shark; the word originally meaning cartilage.) 



ORDEES OF SELACHII IN JAPAN. 



(I. Gill-openings 6 or 7; dorsal fin single; vertebral column imperfectly segmented, 

 each segment l)eing equivalent to 2 vertebra^, and bearing 2 neural arches; anal 



fin present NOTIDANI, I. 



ii((. Gill-openings 5; vertel)ral column well segmented, each segment forming a ni>nral 

 arch and 1 centi'um. 

 /'. Vertebr;e each with the internal calcareous lamelhe radiating from the central 



ring; anal fin present ASTEIK )SI'ONI)Yld, II. 



III'. Vertebnc with the internal calcareous laiiiellic not radiating, but arranged in 

 one or mure concentric circles or series around the (-entral ring; no anal fin; 

 palatoquadrate arch not articulated to tlie skull. 



c. (dll-openings lateral; dorsal fins 2 TECTOSPONDYLl, 111. 



cc. (lill-openings ventral; dorsal fins small and posterior, or wanting; boily and 

 pectoral fins forming a depressed disk BATOIDKI, IV. 



Proceedings U. S. National Museum, Vol. XXVI— No. 1324. 



593 



