17 



MONOGRAPH OF THE GENUS 



HALIOTIS. 



Padollus et Teinotia inclusis. 



Haliotis, Linnceus. — Testa oblique auriformis, plerumque 

 ovata, interdum orbicularis, raro attenuata, versus marginem 

 sinistrum spiraliter angulata, foraminibus plerumque bre- 

 viter tubiformibus uno serie sequentibus, prioribus tectis, 

 ultimis quatuor ad duodecenis apertis perforata ; intus mar- 

 garitacea, extus plerumque spiraliter et interdum concentrice 

 sculpta, varie picta; spira brevissima, aperta amplissima, 

 labio interno arcuato, planato, margaritaceo. — The ear- 

 shaped spiral shell, with a series of perforations on the left 

 side, is too familiar to need description, except as a matter of 

 form. Unlike many other genera, the genus Haliotis is 

 perfectly isolated in its characters, so that it cannot be con- 

 fused with an^' others. The only shells similar in form are 

 found in such genera as Stomatia, Sigaretus, &c., and these 

 have not the series of perforations on the left side so charac- 

 teristic of Haliotis. With regard, however, to the dis- 

 tinction of species, there are few reliable characters to be 

 depended on. For instance, the number of perforations suc- 

 cessively left open in the later stages of growth is no cri- 

 terion, except in one or two possible cases ; and Avlthin the 

 supposed limits of a species there are often nearly as many 

 and as great variations in sculpture, form, convexity, &c., 

 as between it and the nearest allied species. The genus 

 Padollua has been needlessly separated on account of a 

 spiral swelling without, corresponding to a channel within, 

 about half-way between the suture and the ridge of perfora- 

 tions ; and Teinotis on account of its very attenuated 

 form. 



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