HALIOTID^E. 73 



flattened spiral plate. * Muscle-impression horse-shoe shaped, the 

 left branch narrow, inconspicuous, inside the columellar plate, the 

 right branch very large, rounded, situated in the middle of the 

 aperture. 



Animal with a fleshy foot, a fleshy epipodial ridge fringed with 

 cirri, a frontal vail connecting the short eye-stalks ; the mantle slit 

 along the row of holes, branchial cavity containing a gill on each 

 side of the slit. 



The above-defined family constitutes one of the most distinct 

 groups in the Rhipidoglossa, most nearly allied probably to the 

 Pleiirotomariidce. Of the genealogy of the family little is known. 

 A few fossil forms not differing materally from the recent ones have 

 been discovered in the Pliocene and Miocene, and one in the upper 

 cretaceous of Germany. Others will probably be found when the 

 Australian Tertiary and Secondary strata are more fully explored. 



The comparatively slight differences observable among the num- 

 erous recent species, and their distribution, seem to point to a rapid 

 and recent development ; but the isolation of the group as a whole 

 indicates its considerable antiquity. 



The " center of distribution" is in the Australian and adjacent 

 seas. Here are found the greatest number of species and greatest 

 diversity of forms. The largest species inhabit the west coast of 

 North America, but they belong to only two closely allied groups, 

 and probably reached our shores by way of Japan and Alaska. 

 Not one species is found on the east coast of North or South Amer- 

 ica, and only one, H. pourtalesii, on the west coast of the Americas 

 south of Lower California. 



The shells are much used for the manufacture of pearl buttons, 

 buckles and inlaying. On the Californian coast " they are captured 

 by Chinese boatmen, who row along near the rocks, when the tide 

 is low, and peer curiously down into all the cracks and clefts where 

 these great creatures hide. When one is discovered, a wedge on the 

 end of a pole is employed to suddenly dislodge the mollusk from his 

 strong-hold, and a boat-hook draws him up from the water into the 

 hands of the enemy." (Keep, in the Nautilus iv, p. 14.) 



" They are found under stones or in out-of-the-way places among 

 the rocks when the tide is low. All of these mollusks are rock 

 lovers, and it is idle to seek for them except among the crags or 

 broken boulders. It is exceedingly interesting to capture a good- 

 sized fellow and watch his mode of locomotion. When placed on a 



