262 



THE PROTOCHORDATA. 



a U-shaped alimentary canal. Both are deep-sea forms, 

 Cephalodiscus having been dredged during the Challenger 

 Expedition, from the Straits of Magellan, at a depth of 245 

 fathoms ; while Rhabdopleura was first dredged indepen- 

 dently, off the Shetland Islands, at 90 fathoms, by the Rev. 



Fig. 125. — Cephalodiscus dodecalophus, from the ventral side. (.\fter 



M'iNTOSH.) 



Actual length of poh'pide from extremity of branchial plumes to the tip of the 

 pedicle is about 2 mm. 



hj. Buccal shield; the shading on its surface indicates pigment-markin'^s. 

 At the tip of the pedicle, buds are produced. 



Canon Norman, and off the Lofoten Islands, at 200 fath- 

 oms, by Professor G. O. Sars (i 866-68). Rhabdopleura is 

 the name given by Allman ( 1S69), who published a short 

 account of it ; and it has since been described by Sar.-^, 

 Laxkester, and G. H. Fowler. 



