GASTEROPODA. 37 



MnREX ANGULATUS. Woodward. Geol. of Norf. t. 3, fig. 23, 1833. 



ELONGATUS. fig- -2. 



BULBIFORMIS %• 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. IGO, 1843. 



MuREX INCRASSATUS. Nyst. Coq. foss. de Belg. p. 548, pi. 43, fig. 2, 1844. 



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



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

 mbricatd; apice acuminato ; anfractibus 6 — 8 convexis ; aperfurd ovatd; lahro acuta ; 

 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 2\ inches. 



Locality. Red Crag, passim. 



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



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

 wherever a section of that formation is ^dsible. 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. imbricata. 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 cotild not be distinguished. The thick 

 and ponderous variety (fig. 6/^, with rather more elevated and distinct carinae, 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 



