A REVIEW OF THE LANCELETS, HAG-FISHES, AND LAM- 

 rREYS OF JAPAN. WITH A DESCRIPTION OF TWO NEW 

 SPECIES. 



By David Starr Jordan and John Otterbein Snyder, 



Of the Ldand Stanford Junior IhiversUy. 



In the present paper is given an account of the Lejjtocardii and Mav- 

 slpohranchii^ lancelets, hag-fishes, and lampreys, known to inhabit 

 the waters of Japan. It is based on material collected liy the writers 

 in Japan, in the summer of 1900, under the auspices of the Hopkins 

 Laboratory of Stanford University. Series of the species named are 

 deposited in the U. f^. National Museum. 



Class LEPTOCARDII. 

 THE LANCELETS. 



Skeleton membrano-cartilaginous. Notochord persistent and ex- 

 tending to the anterior end of the head, inclosed in a membranous 

 sheath as is the cord-like nervous axis above it. Heart a longitudinal 

 tubular vessel which gives off branchial vessels which unite in an aorta; 

 end of the nervous axis not dilated into a brain and not surrounded by 

 a protective capsule, or skull. Blood colorless. Respiratory cavity 

 confluent with the cavity of the abdomen; gill slits in great number, 

 the water being expelled through an abdominal pore in front of the 

 vent. Jaws none; the mouth a longitudinal fissure, with cirri on each 

 side. Body lanceolate in form, more or less fish-like, and not envel- 

 oped in a tunic. Dorsal fin present, low: anal fin usually more or less 

 developed. 



Small marine animals, highly interesting to the zoologist as exhibit- 

 ing the lowest degree of development of the vertebrate type. The 

 class includes but the single order, Ainphio.fi or Cirrostoini. (XerrTog, 

 thin: Kapdia, heart.) 



Proceedings U.S. National Museum, Vol. XXIII— No. 1233. 



725 



