22 
HEMICHORDATA CHAP. 
has been superseded by Rhabdopleura normani, Allman, based 
Fic. 9.—Cephalodiscus dodecalophus, M‘Tntosh, Straits of Magellan ; A, small portion of 
the common ‘‘house,’”’ x1; @, a single individual, shown also as B,_x 65; six of 
the tentacular arms, belonging to the collar, are seen sprirging from behind the 
proboscis or “ buecal 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. 
