CHAP. VIII. HALIOTIDiE GENERALLY. 2x^9 



been confounded, even by Cuvier, with the true Scuti- 

 branchia, merely because, like them and the Tubuli- 

 hranchin, their mode of generation is the same. If this 

 latter consideration is of such importance, all these three 

 should form one group ; and not only so, but they should 

 be united to the Dyther a, or bivalves, — since they also are 

 fecundated in a similar manner. The fact, however, 

 appears to come out, by analysis, that the HaliotidiB are 

 the representatives of the limpets (Scutibranchia) in the 

 great circle of the phytophagous gastropods, justas^the 

 naked dorises (Nudibranchia) represent the limpets 

 {Scutibranchia) in the entire class of shell-fish (^Testa- 

 cea). And thus, no less a naturalist than Cuvier, from 

 not attending to the two sorts of relationships, — analogy 

 and affinity, — has mistaken the one for the other in both 

 instances, and obscured one of the most beautiful tran- 

 sitions in nature. To this most accurate anatomist, 

 however, we are indebted for the first knowledge of the 

 animal of Haliotis, and to M. Quoy for that of Stomatia.* 

 Without entering into the details, we may simply state 

 that the structure of the first evinces an analogy to that 

 of the PatelUdce, or limpets; while the animal of Stoma- 

 tia still more closely resembles that of the Trochidce, 

 and more especially of Phasianella and Cidaris. The 

 determination of these two facts are of the highest im- 

 portance, since it enables us to discern the two typical 

 groups ; while a beautiful delineation of the S. Chinensis, 

 among the unpublished drawings of Guilding, and of the 

 animal of a Sigaretus by M. Quoy, makes us actually 

 acquainted with the inhabitants of four out of the five 

 genera which compose the family. 



(214.) In regard to the shells of the Haliotid(P, they 

 are easily and certainly recognised : they may be called, 

 indeed, turbinated or spiral limpets, inasmuch as nearly 

 the whole have some slight developement of a spire ; 

 but an indication of the pillar is only seen in that genus 

 which comes nearest to the Trochidce, — namely, Calyp- 



* Stomatella tachetUe, Vov. d' Astrolabe, pi. QQ. bis. 

 Q 3 



