| MUSEUM OF COMPARATIVE ZOOLOGY. 145 
the water-iubes described in other Echinoderms is likewise found in 
Echinarachnius. 
5. The first-formed calcareous deposits of the test in the young Echin- 
arachnius are trifid in shape, varying in number in different specimens. 
The extremity of each trifid division later in its growth bifurcates, and 
the calcareous body thus formed appears to be enclosed in a transparent 
wall, which has a spherical outline. 
6. Spines are very early formed, and are proportionally very large as 
compared with those of the adult, as in other Echinoderms. 
CAMBRIDGE, March, 1886. 
VOL, XII. — No. 4. 10 
