CHAP. VIII. STOMATIA, THE TYPES. 231 



live and die on the very spot where they were originally 

 born ; for the circumference of almost every individual 

 presents a different contour, according to the surface of 

 the substance on which it adhered. Like the Trochidce, 

 we find that the two typical divisions alone are per- 

 laceous. One species of Haliotis is found on our 

 south-western coasts ; but the greater part of these 

 splendid shells, as well as Stomatia, come from warm 

 latitudes. 



(215.) The five primary divisions of the family are 

 only genera, Haliotis and Stomatia being the most 

 typical ; then follow Calyptr&a, Sigaretus, and Cre- 

 pidula. The whole of these constitute a circular group, 

 connected by the third type to the Trochida, and by 

 the fifth to the Neritida by means of Navicella. The 

 scientific reader will find all these groups sufficiently 

 characterised in our arrangement; but a few general 

 remarks appear called for in this place. It is singular 

 that, if any modification in the structure of the animals 

 in Haliotis exist, they are not conspicuously* shown in 

 these shells, with the exception of one, the Haliotis 

 asinina, or ass's ear ; while in Stomatia (of which 

 Quoy has figured the animal of the typical species), the 

 variations in the shell are so many, that there can be 

 little doubt of their being accompanied by a corre- 

 sponding variation in their animals. As we are some- 

 what undecided whether these should all receive sub- 

 generic names (as in the instance of Stomatella), we 

 shall here only mention what appear to be the five 

 types, t S. planulata obviously unites Stomatella to 

 Haliotis, by means of its prototype H. asinina. In both, 

 the spire is very short, the form oblong, and the outer 

 surface smooth. S. auricula seems to be the next type, 

 where the spire is sufficiently developed to be elevated 

 above the surface of the body-whorl ; then comes the 



* Perhaps, however, conchologists have paid too little attention to the 

 Haliotis in the variations of their form. 



t It is curious that Mr. Sowerby, unaware of our views, should have hit 

 upon all these, and urged this variation as a reason for not adopting 

 Lamarck's Stomatella : see his Genera of Shells. 



e 4 



