PURPURA LAPILLUS. 117 



Purpura lapillus (Linnc), and varieties. Plate XI, figs. 1 — 5, 7 — 12, 14 — 17, 



19—23. 



17?8. Buccinmn lapillus, Linne, Syst. Nat., ed. x, p. 739, no. 403. 



1825. Buccinum crispatum, J. Sowerby, Min. Conch., vol. v, p. 12, tab. ccccxiii, figs. 1 — 3. 



1825. Buccinum incrassatum, J. Sowerby, Min. Conch., vol. v, p. 13, tab. ccccxiv, fig. 2. 



1841-70. Purpura lapillus, Gould, Eep. Inv. Mass., ed. 1, p. 301, 1841 ; ed. 2, p. 360, fig. 630, 



1870. 

 1843. Murex iyicrassatns, Njsfc, Coq. foss. Terr. Tert. Belg., p. 548, pi. xliii, fig. 2. 

 1848-72. Purpiira lapillus and varieties, S. V. Wood, Mon. Crag Moll., pt. i, p. 36, tab. iv, figs. 



6a— 6d, 6/, 6cj, 1848 ; 1st Suppl., p. 22, 1872. 

 1853. Purpura lapillus and vars. incrassata and inilricata, Forbes and Hanley, Brit. Moll., vol. iii, 



p. 380, pi. cii, figs. 1—3. 

 1867. Purpura lapillus and vars. minor, major, and imhricata, Jeffreys, Brit. Conch., vol. iv, p. 276, 



pi. Ixxxii, fig. 1. 

 1878. Pohjtropa lapilhis and var. imhricata, G. O. Sars, Moll. Reg. Arct. Norv., p. 250, pl. xxiii, 



fig. 15. 

 1881. Purpura lapillus and varieties, Nyst, Conch. Terr. Tert. Belg., p. 38, pl. iii, fig. 4. 

 1895. Purpura lapillus, Cooke, Cambr. Nat. Hist., vol. iii, p. 90, fig. 35. 

 1900-1. Polytropa lapillus, Br^gger, Norges geol. unders^gelse, vol. xxxi, pl. ix, fig. 7. 



Although the name of P. lapillus occurs in lists of shells from all the Red Crag 

 deposits, the most common variety of that species now living in the North Sea, that 

 given by Jeffreys {op. cit., vol. v, pl. Ixxxii, fig. 1), and in Pl. XI, figs. 21 — 23 of this 

 Memoir, is only known to me from the latest or Butleyan horizon, where, indeed, it 

 is very rare, the Purpuras of the earliest zones grouping themselves with P. incrax- 

 sata, or even with P. tetragona, rather thsin with the typical form. If P. iurrassata 

 were a distinct species — a view adopted by Wood in his 1st Supplement, p. 18 — 

 the specimens figiu^ed by him as varieties of P. lapillus, viz. carlnata, crispata, hrevis, 

 and imhricata, might be regarded as varieties of the former, appearing as they did 

 in the Anglo-Belgian basin at an earlier stage than the existing shell. 



I have figured some prevalent forms of the Purpuras usually grouped with P. 

 lapillus which occur in the Waltonian deposits, in order to illustrate more clearly 

 their connection with P. incrassata on the one hand and P. tetraijona on the other. 



The variety carinata of Wood's Monograph, for example (Pl. XI, fig. 4 of the 

 present work), is merely a dwarf form of P. incrassata (fig. 1) ; his variety imhri- 

 cata (fig. 3) is the same shell with a flounce-like imbrication, while var. eJongata 

 (fig. 14) is similar, with a longer spire; Wood's var. hrevis (fig. 6),^ moreover, 

 belongs to the same group. 



These varieties of P. lapillus connect themselves in like manner with those of 

 P. tetragona ; the spiral sculpture of var. clomjata (fig. 14) resembles that of the 

 variety alveolata of that species (fig. 13) ; another, var. angusta (fig. 19), finds its 

 counterpart in fig. 18, the only difference being that the varix-like ribs are present 



^ Possibly var. minor, Jeffreys, Brit. Conch., vol. iv, p. 277, 1867. 



