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. (After 

 M'lNTOSH.) 



Actual length of polypide from extremity of branchial plumes to the tip of the 

 pedicle is about 2 mm. 



b.s. Buccal shield; the shading on its surface indicates pigment-markings. 



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 (1866-68). Rhabdopleura is 

 the name given by ALLMAN (1869), who published a short 

 account of it ; and it has since been described by SARS, 

 LANKESTER, and G. H. FOWLER. 



