COOKE : ON THE GENUS PURPURA. 323 



Tryon banishes to his index the important fact that P. leii- 

 costoma is a Bourbon shell, described by Deshayes in his 

 'Conch, de 1' He de Re'union,' p. ii6. Nor does he attempt 

 to explain why P. columellaris, a shell confined to a restricted 

 portion of the West Coast of Central America and to the 

 Galapagos, should turn up in the middle of the Indian Ocean 

 and nowhere else. The distribution of the Purpurje is very 

 well marked, and in every case continuous, and not a single 

 example occurs of a break in the area of distribution. This 

 fact alone is decisive of the non-identity of the two species. 

 P. leucostoma has never again been recognised ; it may be 

 doubted whether it is a Purpura at all. 



Page 162. — P. hippocastaneuvi Lam. '■ P. bituhercularis 



Lam. is merely a black variety, it has no distinctive 



characters in the tuberculation.' 



Few will care to follow Tryon in his union of these two 

 species. Indeed, as I have never met a single conchologist 

 who agreed with him on this point, but many who condemned 

 him, it is needless to discuss the matter at length. It is a curi- 

 ous fact that he does not figure the typical hippocastanemn at all. 

 Many of his figures are copied from Kiener, and Kiener figures 

 as hippocastaueuni Lam. an undoubted specimen of bitubercularis. 

 The true hippocastaneum Lam. (that of Linne' being by universal 

 consent incapable of determination) is admirably figured by 

 Reeve, ' Conch. Ic.,' pi. viii., fig. 34c, and differs completely 

 from bitubercularis. This difference is most marked in a point 

 where Tryon says there is ' no distinctive character,' viz., in 

 the tuberculation. The tubercles of hippocastaneum are always 

 more or less foliated, those of bitubercularis never. 



This error naturally involves others. P. savignyi Desh. 

 and P. distinguenda Dunk, are varieties of bitubercularis^ not of 

 hippocasta7ieuin. P. intermedia Kien. is a variety not oi bituber- 

 cularis but of pica Bl. A much worse blunder follows. P. 

 ocellata Kien. is stated to be the young of P. intermedia Kien. 



