114 Mr. Jeffreys on British Mollusca. 



completely changed and mineralized. The geological nature of the 

 rocks of the adjacent coast, according to INIr. Hyndman in his Eeport 

 of the Belfast Dredging Committee (Brit. Assoc. Rep. for 18o7, 

 p 229) is Secondary ; and it does not appear that there are any 

 Tertiary strata in the same locality. For the present, I am still in- 

 clined to consider all the shells of Arctic or Northern species, which 

 have been lately taken in Belfast Bay, as recent. This term is of 

 course comparative in respect of time ; and as the shells of Mollusca 

 are nearly indestructible by the ordinary agencies of air and water 

 (especially when kept continually submerged in the sea, and never 

 exposed to atmospheric influence), the specimens in question may 

 have occupied the Irish sea-bed ever since the commencement of the 

 present geological epoch — viz. for many thousands of years. It is 

 therefore not improbable, for the reasons above given, that Natica 

 clausa, Buccinum HdlbuUii, with other boreal species, will sooner 

 or later be discovered living in or near to the place where the shells 

 now occur. 



Kecluzia aperta. PI. III. fig. 22 a-c. 



Testa globosa, tenuis, cretaceo-alba, epidermide fusco crasso rimato 

 induta, rugis angustis confertis spirahter cincta ; spira brevi, ob^ 

 tusa ; anfractibus 5, couvexis, ultimo spiram superante ; sutura 

 cselata ; apertura rotundata, infundibuliformi, utrinque subeffusa ; 

 peristomate continuo ; labio columellse annexo, reflexo ; columella 

 sinuata, ad basin tuberculo obtuso iustructa ; umbilico parvo, an- 

 gusto, labio fere obtecto ; long. -^-^ unc, lat. eadem. 



This is perhaps the Natica aperta of Loven's Index, p. 1 7, though 

 his comparison of that species with Sigaretus and the Natica Jiava 

 of Gould, as well as certain discrepancies in his description, make me 

 somewhat hesitate before considering my shell to be specifically iden- 

 tical with his. If thev are not the same, I hardly think Loven's 

 shell belongs to the same geims ; and in any case therefore the name 

 I have adopted may serve for my shell. This evidently is congeneric 

 with the Recluzia of M. Petit, which is described in the 4th volume 

 of the ' Journal de Conchyliologie,' p. 117. Of the two species 

 assigned by the author to this genus, I have seen one {R. Rollan- 

 diana) ; but it appears that, of the other species {R. Jehennei), only 

 the typical specimen is supposed to exist. The first of these species 

 came from Mazatlan, and the other from the Red Sea. They are 

 both said to be destitute of an operculum, — a character (although 

 negative) which is common to Loven's shell, as well as mine ; but 

 ]M. Petit states, ou the authority of Captain (now Admiral) Jehenne 

 and Captain Passama, that the animal had a vesicular appendage 

 or float, like that of lanthina. This is remarkable, as the genus 

 is allied, in many respects, to Velutina. Natica Kinyii seems also 

 to have some affinities to this genus, although it differs in the 

 want of an umbilicus and the nature of the epidermis. My speci- 

 men, which appears to be semifossilized, or else in bad condition, 

 was obtained by Mr. Barlee in the last Zetland dredgings. When 



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