44 LUCINIDJE. 



sources of generic distinction, had in this been degraded to 

 a specific position, and that features, usually of little con- 

 sequence, had usurped their places. Until our knowledge 

 of the tribe becomes much more minute and accurate 

 than it now is, conchologists had better content themselves 

 with using a single generic term, than, through a false am- 

 bition of becoming the parents of names, thrust worth- 

 less and embarrassing synonyms on a science already con- 

 siderably encumbered with rubbish. 



As far as external aspect goes, our British Lucina arrange 

 themselves under several sections. Thus, Lucina borealis^ 

 the type of the genus, naturally associates itself with L. 

 spinifera (which constituted the useless genus Myrtea of 

 Turton). To this section, in which, so far as we know, the 

 animal does not exhibit a prolonged anal tube, the name 

 Lucina most especially belongs. The Lucina lactea, and 

 its Mediterranean allies, nearly resemble the former ; but 

 appear to have, judging from the figures of Poli and 

 Deshayes, a very much prolonged anal valve, or tube — this 

 is the section Loripes. The Lucina flexuosa appears to 

 have a very similar animal, though we have not observed 

 its tube ; its shell exhibits peculiarities of dentition which 

 caused Turton to constitute his genus Cryptodon, Phi- 

 lippi his Ptychina, and Leach his Thyasyra. The fossil 

 generic name Axinus had been given by Sowerby to a 

 Lucina evidently of this group, from the London clay, 

 though, as in many fossil genera, the founder seemed to have 

 had a very indistinct notion as to wherein its generic claims 

 and affinities lay. Generic names so founded can scarcely 

 claim right of priority, any more than those of manuscript 

 catalogues, such as the frequently quoted lists of Leach, 

 the publication of one of which by Mr. Gray in the "Annals 

 of Natural History," has not increased, but rather diminish- 



