Mr. W. Clark on Scissurella crispata. 269 



The family Productidce, as will be seen by referring to the 

 table at the end, has been much better represented during the 

 Permian period than was suspected a few years since : in short — 

 of the four known genera, Productus, Aulosteges, Strophalosia 

 and Chonetes^ — we are now acquainted with probably about 

 sixteen Permian species. But what is most remarkable, not a 

 single representative of the family has yet been found in de- 

 posits admitted as belonging to a system more recent than the 

 Permian f. We must not, however, jump to the conclusion, 

 that the family Productidce became extinct at the expiration of 

 the Permian period : there are extensive geographical areas in 

 Asia, South America, Australia and other regions, where beds 

 are developed containing representatives of the family; it is 

 therefore advisable to wait until the exact, or at least the proxi- 

 mate age of the beds referred to be deteruiined, before pro- 

 nouncing that no Productidce lived after the setting-in of the 

 great secondary cycle. 



[To be continued.] 



XXII. — On Scissurella crispata. By William Clark, Esq. 



To the Editors of the Annals of Natural History. 



Gentlemen, Norfolk Crescent, Bath, Febraary 10, 1856. 



The memorandum and figure of Mr. Lucas Barrett, which have 

 just appeared in the ' Annals,' vol. xvii. p. 206, N.S., relative to 

 the animal of Scissurella crispata, is a valuable contribution to 

 malacological science, as it furnishes data to determine with 

 sufficient precision the natural position of this curious species, 

 on which for many years the greatest contrariety of opinion has 

 existed, and which has not been satisfactorily settled until the 

 present time. And I will further remark, that this uncertainty 

 will always prevail when genera are constituted on shell con- 



* Mr. Davidson was the first to work out the affinities of Chonetes : he 

 has proved by its reniform (or ovarian ?) impressions, that it belongs to the 

 family Productidce. Vide Introduction to his ' Monograph of British 

 Fossil Brachiopoda,' 1853. The figure which Mr. Davidson has given of 

 the reniform impressions on the flat valve of a " new species of Chonetes 

 from the Devonian beds of Nehou, in France," proves that this genus is 

 more related to Productus than to Strophalosia, notwithstanding its pos- 

 sessing both teeth and an area. With regard to the so-called Chonetes 

 comoides, its reniform impressions, when discovered, will doubtless settle 

 the question whether it be a Chonetes or a Strophalosia. 



t The so-called Productus Leonhardi (now the type of the genus 

 Koninckia) from the Saliferous rocks of St. Cassian evidently does not 

 belong to Productidce {vide Woodward's excellent ' Manual of Mollusca,* 

 p. 231). I suspect, however, that it belongs, or comes near, to the family 

 Davidsonidce, proposed in my Monograph (pp. 81 & 151). 



