A review of the elasmobranchiate fishes of Japan

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