112 THE ZOOLOGIST. 
SCIENTIFIC SOCIETIES. 
Linnean Soctety or Lonpon. 
February 5, 1889.—Mr. C. B. Cranks, M.A., F.RS., Vice-President, 
in the chair. 
Messrs. J. R. Green and J. W. White were admitted Fellows of the 
Society; and, on a ballot taking place, the following were elected :—The 
Earl of Ducie, Messrs. Henry Hutton and Malcolm Lawrie. 
The Rev. E. S. Marshall exhibited several interesting varieties of British 
plants collected by him in Scotland, and made remarks thereon. 
Mr. E. M. Holmes exhibited a specimen of a new British Marine Alga, 
BRhododermis elegans, Cr., var. polystromatica. Previously this Alga was only 
known to occur at Brest. The discovery of it at Berwick-on-Tweed by 
Mr. E. L. Batters, and at Bognor by Mr. Holmes, therefore extended its 
geographical distribution. The variety found in Britain was new to science, 
since the typical plant was found by Crouan to have only two layers of cells, 
whilst the British plant had several, although it did not otherwise differ 
from the type. 
A paper was then read by Mr. A. D. Michael on three new species of 
parasitic Acari discovered by him in Derbyshire during the autumn of 1888. 
These were a Myocoptes, proposed to be called M. tenax, parasitic on the 
Field Vole, Arvicola agrestis ; a Symbiotes, proposed to be called S. tripilis, 
parasitic upon the Hedgehog ; and Goniomerus musculinus (gen. et sp. nov.), 
a minute parasite found on the ear of the Field Vole. Specimens of all 
three were exhibited under the microscope, and a discussion followed in 
which Professors Mivart, Stewart, and Howes took part. 
Prof. Martin Duncan then gave the substance of an important paper 
which he had prepared, entitled “A Revision of the Families and Genera 
of the Echinoidea, recent and fossil.” . Reviewing the labours of his pre- 
decessors, Prof. Duncan traced the growth of the literature of his subject, 
and showed that although many lists and papers had been published from 
time to time, no general review of the class Hchinoidea had been attempted 
since 1846. Dealing with all the material at his command, he found it 
necessary to propose certain alterations in the classification, and to dispense 
with a good many genera and subgenera, which he considered had been 
needlessly founded. Above all, he had set himself the task of revising the 
descriptions of the genera, giving positive instead of comparative characters, 
a course which he believed would prove of great utility to students. The 
paper was criticised by Mr. Sladen, Prof. Stewart, and Mr. Breeze, all of 
whom testified to the necessity which had arisen for some authoritative 
revision of the subject such as had been undertaken by Prof. Duncan, and 
