22 



HEMICHORDATA 



has been superseded by Rhabdopleura normani, Allman, 1 based 



,/*"* 



B 



FIG. Q.Cephcdodiscus dodecalophus, M'Intosh, Straits of Magellan ; A, small portion of 

 the common "house," x 1 ; a, a single individual, shown also as B, x 65 ; six of 

 the tentacular arms, belonging to the collar, are seen springing from behind the 

 proboscis or "buccal disc." This has a crescentic band of pigment parallel with its 

 posterior border, which conceals the mouth. The stalk, bearing a bud, which 

 already shows the beginning of two tentacular arms, is seen to the right. (After 

 M'Intosh, B from Parker and Haswell.) 



1 Allman's name (Quart. J. Micr. Sci. ix. 1869, p. 57 f.) replaces that given 

 by Sars, because the latter gave no description by which the organism could be 

 recognised. 



