GASTEROPODA. 37 



Murex angulatus. Woodward. Geol. of Norf. t. 3, fig. 23, 1833. 



— ELONGATUS fig. 22. 



BULB1FORMIS fig' 21. 



LAPILLIFORMIS fig. 25. 



— COMPRESSUS fig. 26. 



Purpura lapillus. Flem. Brit. An. p. 341, 1828. 



— Gould. Invert, of Massachusetts, p. 301, 1841. 



— Thorpe. Brit. Mar. Conch, p. 212, 1844. 



— S. Wood. Catalogue 1842. 



— Morris. Catal. of Brit. Foss. p. 160, 1843. 



Murex incrassatus. Nyst. Coq. foss. de Belg. p. 548, pi. 43, fig. 2, 1844. 



— Dale. Hist, and Antiq. of Harwich, tab. 10, fig. 4, 1730. 



P. Testa ovatd, vel elongatd, ventricosd, crassd, transversim sulcata, longitudinaliter 

 imbricatd ; apice acuminato ; anfractibus 6 — 8 convexis ; aperturd ovatd ; labro acuto ; 

 columella planiuscula ; canali brevi. 



Shell variable, ovate, elongate, ventricose, angulose, compressed, thick, and 

 strong, transversely sulcated or ridged, longitudinally imbricated ; whorls 6 — 8, 

 convex ; outer lip sharp, sloping inwards where it is thick and denticulated, with a 

 broad and flattened columella ; canal short, and a small but open umbilicus. 



Axis, reaching 2f inches. 



Locality. Red Crag, passim. 



Mam. Crag, Bramerton and Thorpe. — Recent, Britain and N. America. 



This is one of the most abundant fossils of the Red Crag, and may be obtained 

 wherever a section of that formation is visible. It is exceedingly variable, and no 

 dependence can be placed either upon proportionate dimensions or upon the angle of 

 volution. In some specimens the aperture measures two thirds the entire length of 

 the shell, while in others it is not more than two fifths. I have little doubt but the 

 shells figured by Woodward, above referred to, are deformed specimens of one 

 species produced by the same cause, to which I have assigned, in my Catalogue, the 

 many different varieties of the Littorina littorea. Dr. Gould appears to have divided 

 the American shells into two groups, those which are smooth and thick, as the true 

 lapillus, and the imbricated ones, which have a rather longer canal, and were 

 considered by Lamarck as a distinct species, under the name P. vmbricata. The 

 surface of all the specimens from the Crag, when in good condition, are covered 

 with imbrications, which induced the author of ' Min. Conch.' to consider it distinct ; 

 but the recent British species is found sometimes with quite as rough a surface, and 

 specimens in my cabinet are so precisely similar to some of the fossils that, except 

 in colour, they could not be distinguished. The thick and ponderous variety (fig. 6 //), 

 with rather more elevated and distinct carinas, figured and described in ' Min. Conch.' 

 as P. incrassata, is rather an aberrant form in this species, but may be connected by 

 a large series of specimens ; and several able conchologists, who have examined 

 the varieties I possess, are of the same opinion, that it is only an extreme form. In 

 the Crag seas it appears to have attained a greater magnitude than the generality of 



