GASTEROPODA. 27 
and retains only the faintest traces of tubercles ; the axial umbilicus is very conspicuous ; 
and all trace of the wide basal notch being lost, the aperture resembles an entire- 
mouthed shell. The hard limestone being much used for rough walls, it is upon these, 
when partial disintegration has taken place, that the casts of Purpuroidea are to be found. 
The genus has never been discovered lower than the planking. 
Purruromea Morgavsia. Plate IV, figs. 1, la, 2, 3, 3a, 4. 
Purpura Morzausia, Buvignier. Mém. Soc. Philomath. Verdun, 1843, pl. 6, fig. 19, 
p- 26. 
PurPuRINA — D’Orb. Prod. Paléont., p. 357, 1850. 
P. Testa turrita, globosd ; spird brevi, anfractibus 3—A, nodulosis vel spiniferis ; spinis 
magnis, obtusis, in serie unicd 7, 8, aut 9 in ambitu ; anfractu ultimo striato, striis regu- 
laribus transverse subundulatis (obsoletis in etate seniori) ; apertura anipla, subquadrata ; 
canali dilatato, leviter excavato. 
Shell globose, spire prominent, whorls 3—4, angulated ; angles tuberculated ; tubercles 
large, elevated, 8 or in others 7, upon a volution ; the last whorl ventricose ; the tubercles 
increasing in size until they become large blunt spires; beneath the tubercles the surface 
has numerous undulating closely-arranged encircling costae; the aperture is large and 
widely truncated at its base; the inner lip is somewhat depressed in its middle part. 
This is by much the most abundant, and at the same time typical species of the genus. 
There may be considered to be two varieties, one having 8, the other only 7, spines in a 
volution ; the latter variety has the spire more depressed, the aperture occupying three 
fourths of the entire length of the shell. The elevated longitudinal swellings, produced by 
the successive extensions of the outer lip in growth, sometimes interfere with the continuity 
of the encircling ribs,—cause them to undulate, and occasionally obscure them altogether 
hence, in the younger specimens, the ribs are more regular and distinctly marked. Very 
rarely, indeed, individuals have been found which simulate P. nodulata, the lines of growth 
being enlarged to imperfect ribs, which suddenly disappear, or are depressed at the place 
where, in the species referred to, the second circle of nodules is situated; the spire also 
becomes more elevated, which adds to the resemblance. In the figure given by Buvignier, 
the inner lip is more flattened, or Purpura like, than might have been expected; but the 
figure altogether is executed in a very indifferent manner. 
Locality. The vicinity of Minchinhampton is the only locality in which this remarkable 
shell is known to have been procured in England. Buvignier mentions that M. Moreau, 
of St. Mihiel, has found it in the Coral rag of that place, and likewise in the ferruginous 
Oolite of Launoy. 
