BUSK, ON DR. WALLICH’S MICROSCOPIC “ JAW.” 39 
+) 
weight, suggests that the so-termed “jaw” may be the dac- 
tylos,or moveable claw of a minute crustacean (Phrosina). 
But, with all due allowance for the circumstance that this 
opinion appears to have been based only upon the inspection 
of the original very faulty figure given by Dr. Wallich, it 
seems to me that, even with this allowance, an insuperable 
objection to Mr. Spence Bate’s view would arise from the fact 
that the “second row of marginal armature” is really placed 
as if it were the second ramus of an actual jaw, and not, as 
he erroneously interprets or appears to interpret the figure 
(‘Ann Nat. Hist.,’ x, p. 304), in the same line or plane, but 
above the first row, as I understand him to mean. 
There can be, no doubt, as he or any one would see on a 
glance at the specimen itself, that the two serrated margins 
are placed one behind the other, as the alveolar borders of a 
jaw would be. This being the case, it is needless, I should 
fancy, any longer to entertain the question of the object being 
the claw of a crustacean, in which the serrations or denticles, 
if there be any, are always placed in a single median row. 
But having negatived this view, upon what grounds is the 
thing to be regarded as the valve of a pedicellaria? This 
may be explained in a few words, and will, I hope, be found 
to be satisfactorily elucidated by the adjoined figures. Of 
these, fig. 1 represents the ‘jaw’ as it is exhibited in Dr, 
Wallich’s preparation, in which the object is unfortunately 
a good deal obscured by foreign matter. Fig. 2 is the side view 
of a valve of the pedicellaria of Echinus lividus, of which some 
