17G Oeological Society. 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



June 19, 1889.— Prof. J. W. Judd, F.R.S., 

 Vice-President, in the Chair. 



The follcwing communications were read : — 



1. " The Descent of /S'owm'nm and oi Hammatoceras" By S. S. 

 Buckman, Esq., E.G.S. 



The Author reviewed the history and literature of the genus 

 Sonninia, Bayle, which was founded to receive the Ammonites of the 

 Soiuerbi/i-gro\ii:>, formerly classed, together with those of the Insig- 

 ms-group, in the genus Hammatoccras. 



The reasons why the genus Sonninia is not descended from 

 Hammatoceras, or from Haugia (Variahiiis-gToi\Y>), were set forth. 

 Then, proceeding to trace out the life-history of Ph'uroceras, 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 Hammatocerns, 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 Ilammatoceras 

 was taken to justify the separation of the former from the latter. 

 The genus Sonninia would be correctly placed in the family 

 Amaltheidse ; while the genus Hammatoceras would be placed in the 

 same family as Steplianoccras. 



Of the numerous new species belonging to the genera Sonninia 

 and Ilammatoceras, certain forms, necessary to elal)orate the ideas 

 set forth above, were described and definitely separated. The paper 

 also touched upon certain other facts connected with Ifammatoceras, 

 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 the characters of the genus Ortlionema, 

 Meek and "Worthen, the following forms were described: — Ortlio- 

 nema pi/gmaa, n. sp. ; 02, n. sp. ; Murchisonia turriculaf a, do Kon, 

 (Yorcdalo Shales, Askrigg, Yorkshire) ; 31. turriculata, var. scotica ; 

 and M. compacta, n. sp. 



