lU 



THE GEOLOGIST. 



young ; but this of course must remain, for the present at least, one 

 of those uncertainties with which the science of Palaeontology abounds ; 

 and I can quite concur with Mr. Toulmin Smith as to the necessity of 

 carefully considering what we give out as facts ; for indeed the word 



certain" has been more often made use of where that of " probable" 

 would have been more properly written. 



In conclusion, whether it be desirable to retain some or all of the 

 denominations or subdivisions in the Productidse, no doubt can exist 

 as to their intimate relationship. 



Producta is supposed to have been always deprived of hinge-teeth 

 and sockets for the articulation of the valves j and although this is 

 the condition in all species hitherto examined, there may possibly have 

 existed some exceptions. No distinct area is visible in the generality 

 of species, but in certain specimens it is known to exist. Aidodeges 

 has been considered by some as a synonym of Stmphcdosia, but the 

 want of hinge-teeth and the great similarity of its interior details 

 with those of Froducta, makes me consider it even more closely con- 

 nected with the last-named genus than with that of Professor King j 

 or, in other words, that it is the connecting link between them. 



Sirophalosia and Chonetes are distinguishable from Producta by the 

 invariable presence of hinge-teeth and sockets, as also by a distinct 

 area in either valve, and by other minor interior details. Stroplialosia 

 was fixed by a portion of its larger valve, while Chonetes was probably 

 free, and is in general recognizable by the position and disposition of 

 its cardinal spines.* 



In Notes No. 3 we will endeavour to describe and illustrate the 

 character of the Strophomenidce. 



* Those wlio may feel desirous for more ample information concerning the 

 Productidc>3, will do well to consult Prof, de Koninck's excellent " MonogTapliie 

 des Genres Productus et Chonetes, Liege, 184:7 ;" also the second volume of the 

 " Geology of Russia, in Europe and the Ural" (1845) ; Count KeyserHng's 

 " Petschoraland" (184G) ; King's " MonogTaph of the Permian F'ossils of 

 England" (1850) ; Sowerby's " Mineral Conchology ;" Woodward's " Manual of 

 the Mollusca," and various other works and papers by M]M. de Verneuil, Geinitz, 

 Kutorga, Martin, and Howse, as well as the three editions of my General 

 Introduction," &c. In my " JMonogTaph of British Permian Brachiopoda," pub- 

 lished in 1858, the subject has also been attentively re-examined ; and it may not 

 here perhaps be considered out of place for me to remark, that during the careful 

 preparation of that work, Avhich occupied the greater portion of my time during 

 one year and a half, I did my very utmost to be just and fair towards all con- 

 cerned, allowing no bias or preference to interfere with my judgment ; and 

 although I may be mistaken with respect to certain scientific questions, I have 

 not hitherto perceived any valid grounds for altering the conclusions therein 

 expressed. 



