365 
study of these forms is that they are beyond doubt separate 
species all of them, good distinguishing characters being affor- 
ded by the calcareous bodies of the skin as well as by the calca- 
reous ring. 
Figs. 46.a — c. represent the calcareous bodies of the three forms. 
C. australis is seen to differ from the two others in entirely lacking 
Fig. 46. Calcareous bodies, in front and side view, of Caudina clillensis (a), C. coriacea 
(b), and C. australis (c), 
the characteristic x-formed elevation in the middle of the plates; 
there are several irregular holes and both sides are rather spiny. 
C. coriacea is more like chilensis in regard to these calcareous 
plates, but they are decidedly more thorny in chilensis than in 
coriacea. No less marked differences are found in the calcareous 
ring (Figs. 47.a—c). C. chilensis has long and narrow interradials 
with a distinet median keel, and the radials have three prominences 
on the anterior margin, one median and two lateral ones.^) C. 
coriacea has short broad interradials, without a longitudinal keel; 
the radials have only two lateral prominences on the anterior 
margin, being coneave in the middle; they are also characteristic 
through being distinetly narrowed off the posterior end of the inter- 
} radials, while in the two other species there is no such distinet 
• narrowing. In C. australis the interradials are intermediate in form 
between those of chilensis and coriacea, while the radials are 
1) This also holds good of C. rugosa Perrier, be this Chilenian form iden- 
tical with C. chilensis or a separate species, a question which need not 
concern us here, seeing that it is, at any rate, different from the New 
Zealand species. 
3 
L 
