40 BUSK, ON DR. WALLICH’S MICROSCOPIC “‘ JAW.”’ 
3 
mounted specimens have been kindly furnished by Dr. Wallich, 
whilst fig. 3 shows the corresponding part of the pedicellaria 
of a species of Amphidotus, as 1 am informed by Mr. R. 
Beck, to whom I am indebted for the illustration. The figures 
of several other pedicellarian valves might have been added, 
all differing more or less inter se, though agreeing in essential 
structure; but I have thought the above examples would be 
sufficient for the present purpose. I would remark, however, 
in passing, that a full account and accurate figures of the va- 
rieties which exist im the pedicellariz of various Echinidze 
and Asteride, would afford a subject for a very useful and 
interesting paper, and might assist, perhaps, very considerably, 
in the discrimination of species or genera in those families. 
In those cases that I have examined, and probably in all, 
the pedicellariz of the Echinide consist of three valves, arti- 
culated apparently in a complex manner to each other, and 
furnished with appropriate processes for the attachment of 
the muscles by which they are moved. It is not my intention, 
nor, in fact, in my power, to describe fully the mechanism of 
these organs, but simply here to poimt out in a few words the 
essential pomts regarding them, so far as they throw light 
upon the structure of the “ jaw.” 
Each valve consists of a spoon-shaped distal portion, at the 
base of which is a strong, curved, arched process, like a door- 
knocker, and on either side of the same part an irregular pro- 
cess or condyle, by which the valve appears to be connected by 
a ligamentous tissue with those next toit. Viewed on the inner 
or concave side, the valve will be seen to be strengthened by 
a prominent median ridge or kelson, from which a ridge passes 
off obliquely forward on each side, nearly to the edge of the 
spoon-shaped portion. This kelson posteriorly or towards 
the base of the valve, rises into a strong, bluntly-toothed pro- 
cess, generally, I believe, connected to the sides of the base, 
or to the external condyles above mentioned, by a slender 
calcareous arch. To this rough eminence of the kelson I 
conceive the occlusor muscles or muscle to be attached, whilst 
the dilators are doubtless inserted in the door-knocker 
appendage below. The anterior part of the kelson some- 
times also supports one or more sharp denticles,* but 
in some cases, as for instance, I think, in Echinus sphera, 
* Thad entirely overlooked the median tooth in the “jaw,” and was 
quite unaware of the occurrence of any in that situation, in other Pedicel- 
lari, until it was pointed out to me by my friend Mr. R. Beck, to whose 
quick sight and ready assistance J am much indebted on the present as I 
have been on other occasions. 
