176 Geological Socrety. 
PROCEEDINGS OF LEARNED SOCIETIES. 
GEOLOGICAL SOCIETY. 
June 19, 1889.—Prof. J. W. Judd, F.R.S., 
Vice-President, in the Chair. 
The following communications were read :— 
1. “The Descent of Sonninia and of Hammatoceras.” By 8. S. 
Buckman, Esq., F.G.S. 
The Author reviewed the history and literature of the genus 
Sonninia, Bayle, which was founded to receive the Ammonites of the 
Sowerbyi-group, formerly classed, together with those of the Jnsig- 
nis-group, in the genus Hammatoceras. 
The reasons why the genus Sonninia is not descended from 
Hammatoceras, or from Haugia (Variabilis-group), were set forth. 
Then, proceeding to trace out the life-history of Pleuroceras, Amal- 
theus, and Sonninia, as shown by their inner whorls, the Author 
arrived at the conclusion that these three genera were descended 
from a common source, and that they form three branches from one 
stem. 
The development of the genus Hammatoceras, sensu stricto, was 
then traced out, and its descent shown to be from the genus 
Deroceras, which is in accordance with the general ideas upon the 
subject. 
The difference in the descent of Sonninia and Hammatoceras 
was taken to justify the separation of the former from the latter. 
The genus Sonninia would be correctly placed in the family 
Amaltheide ; while the genus Hammatoceras would be placed in the 
same family as Stephanoceras. 
Of the numerous new species belonging to the genera Sonninia 
and Hammatoceras, certain forms, necessary to elaborate the ideas 
set forth above, were described and definitely separated. The paper 
also touched upon certain other facts connected with [/ammatoceras, 
Sonninia, and cognate genera. 
2. “ Description of some new Species of Carboniferous Gastero- 
poda.” By Miss Jane Donald. (Communicated by J.G. Goodchild, 
Esq., F.G.S.) 
The Gasteropoda described in this paper have, with one exception, 
been collected by Mr. John Young from the Upper Limestone Series 
of Scotland. After discussing she characters of the genus Orthonema, 
Meek and Worthen, the following forms were described :—Ortho- 
nema pygmea, n. sp.; 02, n. sp.; Murchisona turriculata, de Kon. 
(Yoredale Shales, Askrigg, Yorkshire) ; ; M. turriculata, var. scotica ; 
and M, compacta, n. sp. 
