SCIENTIFIC SOCIETIES. 33 
Mr. C. Stewart demonstrated, under the microscope, the stridulating 
apparatus of a species of Spharotherium, differing in some respects from 
that described by Mr. Bourne (infra). 
Dr. J. Murie exhibited and made remarks on the caudal end of the 
spine of a Haddock with an arched deformity, recalling what is recorded of 
the so-called Hump-backed Cod, Morrhua macrocephala. 
Prof. P. M. Duncan read a paper on the “perignathic girdle” of the 
Kchinoidea. The author maintained that as the structures which give 
attachment to the muscles that protrude and retract the jaws of the 
Kchinoidea (which are parts of the test surrounding the peristome 
within) are not homologous in all the families of the group, it is not 
advisable to retain the old name of “auricles.” He would substitute 
the term “ perignathic girdle.” The girdle consists of processes usually 
united above (though occasionally disconnected), and of “ridges” which 
connect the processes on the side remote from the ambulacra. ‘The ridges 
are modifications of the inter-radial plates, the processes developments from 
the ambulacral plates. In the Cidaride the muscular attachments are all 
on disconnected ridges, and there are no processes. In the Temnopleuride, 
Echinide, Echinometride, and Diadematide, the retractor muscles are 
attached to ‘“‘ processes,” which are growths of the poriferous portions of the 
ambulacral plates; and the protractor muscles and ligament of the radiales 
are attached to the ridge which is developed on the inter-radial plates, aud 
is united by suture to the base of the “process.” In the Clypeastride 
there are discounected growths, which carry the jaws, and have slight 
muscular attachments. In Clypeaster there are ten processes, each arising 
from an ambulacral plate; and there are no inter-radial structures like 
ridges. In Laganum there are five growths, each arising from a first inter- 
radial plate; hence these are the homologues of ridges. The Clypeastride 
may thus be divided into two groups, on account of the presence of processes 
in one, and of the homologues of ridges in the other. 
Prof. Moseley communicated a paper on the anatomy of Spherotherium 
by Mr. Gilbert C. Bourne. The author remarked that while the general 
external features and specific distinctions of the genus had been amply dis- 
cussed, the internal structure had hitherto received scant attention. 
Among other anatomical peculiarities he described a well-defined stridulating 
organ in the male. This consists of a prominent bolster-shaped swelling on 
the postero-external edge of the secoud joiut of the second pair of copulatory 
appendages. The swelling occupies the entire margin of the joint, and 
shows a number of chitinous cross ridges and furrows. On the opposite 
interior surface of the last tergite are chitinous points. The former rasp- 
like organ of the second accessory appendages, when rubbed rapidly against 
the latter, produces a shrill note resembling that emitted by the House 
Cricket. A true auditory organ exists in the antenuary fossa beneath the 
ZOOLOGIST.—JAN. 1886. D 
