28 



GASTEROPODA. 



great antiquity, the latter being exclusively Palseozoic, and 

 the former mainly so. 



The genus Haliotis (fig. 414, c) comprises the so-called 

 " Ear-shells," distinguished by their ear-shaped shell, with a 



Fig. 4'-l. — A, Iiuclias conulus — Pliocene; b, riumanella inelanoides — Eocene; c, IlaUotis 

 ii(be;-(M(tata— Pliocene ; d, Scissurella aspc7-a— Pliocene ; e, Scalitcs angidatus — Lower Silu- 

 rian ; F, Trocliotonm ci^nis— Jurassic. (After Searles Wood, Dcshayes, Pictet, Pliilippi, and 

 Hall.) 



minute spire, an enormous aperture, and a series of round 

 perforations in the outer angle of the shell. A few fossil 

 species are known, commencing in the Miocene. 



Stoniatia is allied to Haliotis, but the spire is prominent, 

 and the place of the perforations in the shell is taken by a 

 furrow. The genus forms a transitional link between the 

 families Haliotidce and Turhinidcc, and is represented by 

 living forms, the earliest types ascribed to it dating from the 

 Devonian. 



In the genus Scissurella (fig. 414, d), which also com- 

 mences in the Pliocene, the shell is thin, with a large and 

 greatly expanded body-whorl, and the place of the perfora- 

 tions of Haliotis is taken by a simple slit in the margin of 

 the outer lip. 



