290 PROCEEDINGS OP THE MALACOLOGICAL SOCIETY. 



Besides describing the above species in the "Descriptive Catalogue," 

 Gray also split up the genus Cyprcea, making the genera Luponia and 

 Trivia and the subgenera Aricia and Naria. All with the exception 

 of Trivia, which is now shown to be a good genus, are simply 

 sections of Cyprcea. Their authors, and the place where first adopted, 

 are as follows : Luponia and Trivia, Sowerby, " Conchological 

 Manual," 1839, pp. 60, 108; Aricia, H. & "A. Adams, "The 

 Genera of Recent Mollusca," 1854, vol. i, pp. 265, 266; A'aria, 

 Gray, "Guide to the Systematic Distribution of Mollusca in the 

 British Museum," 1857, pt. i, p. 72. It will be observed that the 

 dates of various species in the "Conchological Illustrations" quoted 

 in this paper, differ from those which have hitherto been considered 

 correct. The dates now cited may, however, be regarded as accurate, 

 as proved by certain information lately acquired (■vide my paper on 

 the " Conchological Illustrations," which will be published in Part VI 

 of this volume). 



I now give some notes on the differences between Cyprcea and 

 Trivia, and the reasons for considering them distinct genera. 



In 18.39 Sowerby, on conchological grounds, created the genus 

 Trivia for that section of Cyprcea which is characterized by a lighter 

 shell, with ridges or costse running transversely from the base over 

 the sides and dorsal surface, ending in most cases in a groove or 

 sulcus, sometimes broad and shallow, or narrow and deep, running 

 longitudinally along the centre of the shell. In some species there is 

 no sulcus, and the striae gradually become less and less until thtsy 

 disappear on the middle of the dorsum, while in others tliey interlace 

 so that the striae from one side end in the grooves between those of 

 the other. 



Some writers have considered Trivia as a genus, others as a subgenus, 

 while a third class maintain that it is simply a section of Cyprcea. 



When about to revise the nomenclature of the latter genus, this 

 matter was of great importance, because if they were dislinct genera 

 they might have the same specific name standing in each, and the 

 nomenclature of one would not interfere with that of the other. On 

 the other hand, if Trivia was only a subgenus or section, a good many 

 names would have to be altered as having been used in the one group, 

 although perhaps now only being synonyms of earlier names, but in 

 the other group there were shells bearing these same designations 

 which would have had to be changed. 



If Trivia was made a genus on purely conchological differences, 

 there was no reason why Luponia, Naria, Cyprmovula, Aricia, 

 Qashoinia, etc., should not also be considered as genera, as they differ 

 conch ologically from the typical C. mappa, Linn., almost as mnch as 

 Trivia. 



After consulting Mr. E. A. Smith on this subject, it was decided 

 that if any real anatomical difference existed between Cyprcea and 

 Trivia it would be justifiable to regard them as distinct genera, weight 

 also being given for this decision by the difference of the shells. 



Mr. H. G. Farmer, New College, Oxford, to whom I am greatly 

 indebted for all the trouble and time he has expended over the matter, 



