THE G-EOLOGIST 



MARCH, 1859. 



PAL^ONTOLOGICAL NOTES ON THE BRACHIOPODA. 

 By Thomas Davidson, Esq., F.R.S., F.G.S,, etc. 



No. 2. On the Families STROPHOMENiDiE and Productid^. 



In my last communication, I endeavoured to lay before the reader 

 all the more important facts, already acquired, relative to the genera 

 and sub-genera that are provided with spiral appendages for the 

 support of the oral arms ; * and at the same time I referred to 

 several points which still required to be elucidated and explained 

 before the subject could be considered to have been satisfactorily 

 studied. 



In a note at the conclusion of that paper, allusion was made to a 

 well-preserved internal cast of Cyrtina septosa, of which I now offer 

 a representation, as it will show that the muscular impressions in the 

 smaller or dorsal valve are similarly arranged to those of Sinriferaj 

 and that there does not exist in that valve any septa, as in Pen- 

 tameru$ ; the resemblance to the last-named genus being merely in 

 the disposition of the median septum, and of the converging dental 

 or rostral plates of the larger or ventral valve. 



I may likewise mention, before commencing the subject of the 

 present communication, that, although the muscular impressions in 

 the larger or ventral valve of Athyris or Spirigera are generally well 



* The Geologist, vol. i. p. 409. 1858. This paper has been translated into 

 French by my friend Professor L. de Koninck, and will be published in the 

 Transactions of the Royal Society of Liege, for 1859. 



VOL. II. H 



