615 
of Edinburgh, Session 1871-72. 
The following Gentlemen were admitted Fellows of the 
►Society:— 
David Maclagan, Esq., C.A. 
Major Rickard. 
Dr John Sibbald. 
Dr J. G. Fleming. 
Rev. Andrew Tait, LL.D. 
David Grieve, Esq. 
The Right Rev. Bishop Cotterill. 
George Barclay, Esq. 
Monday , 29 th January 1872. 
The Hon. LOED NEAVES, Vice-President, in the Chair. 
The following Communications w T ere read :— 
1. On the Wheeling of Birds. By Professor Fleeming 
Jenkin. 
2. Notice of a New Family of the Echinodermata. By 
Professor Wyville Thomson, LL.D., F.E.SS.L. and E., 
F.L.S., F.G.S. 
During the deep sea dredging expedition of H.M. ships 
‘ Lightning ’ and ‘Porcupine,’ in the summers of 1868-69 and 
1870, two or three nearly perfect specimens, and a number of frag¬ 
ments were procured of three species of regular echinideans, which 
were referred by the author to a new family, the Echinothuridse, 
intermediate in their more essential characters between the 
Cidaridse and the Diadematidse. 
In these urchins the test is circular and greatly depressed. The 
plates of the perisom are long and strap-shaped, and the inter- 
ambulacral plates overlap one another regularly from the apical 
towards the oral poll, while the ambulacral plates overlap in a 
similar way in the opposite direction. The test is thus flexible. 
The plates of the ambulacral arern are essentially within the inter - 
ambulacral plates which over-lie them along their outer edges. 
The ambulacra! pores are tri-gem inah arranged in wide arcs; the 
