498 Mr. Jeflfreys on British Mollusca. 



not, however, to allow your readers to suppose that I founded the 

 genus Jeffrexjsia ; and I should be sorry to be deemed capable of 

 such an egregious act of vanity as to affix my own name to any genus 

 or species. 



Euomphalus nitidissimus. It is scarcely worth while contrasting 

 the drawing (fig. 16. pi. 3. Ann. ser. 3. vol. iii.), which is confirmed 

 by that of M. Deshayes, of a living and active animal with the sketch, 

 made by a lady-artist for Mr. Clark, of the dried remains of another 

 animal of the same kind. What Mr. Clark supposed to be tentacula 

 must have been the shrivelled lobes of the veil, although it is not 

 quite clear what he means by the " veil ;" for in one part of his re- 

 marks (p. 410) he considers it to be synonymous with the "anterior 

 part of the head," while in the next page he identifies it with the 

 " mantle." Dr. Gray has clearly pointed out, in the 'Annals ' (ser. 2. 

 vol. xvi. p. 422, and same series, vol. xviii. p. 419), that Truncatella 

 and Assiminia are totally different animals, especially in the form of 

 the tentacula and position of the eyes. The shells in every case 

 correspond with the animals. As to the form of the aperture of the 

 shell, it must be borne in mind that, although Euomjihalus pent- 

 angulatus is the typical species, the aperture in many other species 

 of that genus is suborbicular, while E. Rota, and especially the variety 

 tricarinata of Webster, has the aperture slightly subangular. Mr. 

 Clark does not take any notice of the peculiar tongue or lingual 

 riband of this curious mollusk — a character which is admitted by all 

 good conchologists to form an essential element of generic distinc- 

 tion. With respect to the question whether these tiny creatures can 

 properly be referred to the extinct genus Euomphahis, which con- 

 tains species of a comparatively much larger size, I will subjoin an 

 extract from Sir Roderick Murchison's invaluable work, ' Siluria ' 

 (3rd ed. p. 464), in which he says, as to Pterygotus Anglieus and 

 P. prohlematicus, " In the ' Quarterly Journal of the Geological 

 Society,' vol. xii. p. 28, Professor Huxley has given reasons for con- 

 sidering these great Crustacea (the former estimated to have been 

 7 or 8 feet in length !) to be of a type nearly resembling some of the 

 smallest of our living Decapod Crustacea {Alauna, Bodotria, Cuma, 

 &c.), and as even showing great similarity to the larval state of the 

 higher forms." This is a very suggestive idea, which may lead to 

 most interesting and important results. In the event of its being 

 considered advisable to form a new genus for the reception of these 

 anomalous mollusks, I would venture to propose the name of Omalo- 

 gyra. 



In answer to Mr. Clark's remarks on the species of Odostomia or 

 Chemnitsia, it appears to me quite a waste of time to go again over 

 the same ground ; but I may observe that a card of shells which he 

 obligingly gave me as a variety of Odostomia acuta, contained also 

 several O. t%irrita or striolata, which difi'ers from the first-named 

 species in having a blunt instead of a tapering and sharp-pointed 

 spire, in the penultimate whorl being rather prominent (giving the 

 shell a somewhat fusiform appearance), in the contracted aperture, 

 in being spirally striated, and especially in wanting the distinct and 



