CHAPTEE VIII 



CEPHALOCHORDA 



Phylum VERTEBRATA 



Sub-Phylum ACRANIATA 



Class UROCHORDA Type 



CEPHALOCHORDA . . Amphioxus 



THE Acraniates include the Ascidians, and Amphioxus and 

 Epigonichthys, which two genera constitute the Cephalochorda. 

 Both classes are marine, and are related to the Hydrocoela, 

 which are also marine. Amphioxus presents lowly vertebrate 

 features, features which are passed through in the develop- 

 ment of the craniates, in addition to others which are incor- 

 porated in association with its lowly vertebrate structure and 

 its manner of life. 



Amphioxus lanceolatus is common in shallow water in 

 certain regions in the Adriatic, at Messina, Naples, and other 

 parts of the Mediterranean, in the western region of the English 

 Channel, in the Heligoland Bight, in the Cattegat, and it has 

 been observed at various places on the west coast of Norway 

 up to Trondhjem. It was obtained during a Government 

 survey in 1921 on the Dogger Bank. It occurs on the Atlantic 

 coast of America and has been recorded from Ceylon. Other 

 species are found in tropical and temperate seas generally, so 

 that the genus is world-wide in distribution, and the species 

 are very similar in structure. 



EXTERNAL MORPHOLOGY. Amphioxus lanceolatus is small ; 

 it measures scarcely two inches long when fully grown. In the 

 living state it is transparent and has a fleshy tint. It burrows 

 in sand and comes to rest in an upright position with the mouth 



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