P. F. Kendall—Aragonite Shells in the Ooralline Crag. 499 
there need be no difficulty if attention be paid to the point I have 
indicated. 
Mr. Sorby mentions as examples of Gasteropods having a calcite 
layer, Fusus, Purpura, Littorina, and Patella; but he informs me 
that he has not tested Scalaria. This accords exactly with what 
I have observed in the Crag beds, but to the genera named above I 
would add Tectura and Murex (M. tortuosum). The Fust are very 
interesting, the genus is not very clearly divided from Trophon, and 
hence errors may arise, but the species of Fusus occurring in the 
Crag which appear to have a calcite layer are F. antiquus, I. scalari- 
formis and F. Berniciensis. Fusus altus, F. costifer, F'. muricatus, F. 
cordatus and F. gracilis, have no calcite layer preserved, and I do 
not think that the first two ever possessed any, but #. gracilis in 
the fresh condition certainly looks like a calcite shell. It is a fact 
worthy of notice that in those Fusi which have a calcite layer the 
first two volutions are destitute of it. This suggests the question :— 
Ts not this embryonic condition indicative of descent from an 
ancestor which was devoid of a calcite layer? All those Eocene 
species of Fusus, such as F. longevus, bulbiformis, and pyrus, which 
I have examined, appear to be entirely aragonite. Two species of 
Littorina occur in the Crag beds, viz. L. littorea and L. suboperta, the 
former has a thick calcite layer, but I have never seen a trace of one 
in L. suboperta. I cannot however say that it may not have had 
one, for the specimens are so much worn. 
I have been somewhat surprised to note that among the hundreds 
of calcite shells which I have collected among the Crags, I have 
never come across any which were bored by Carnivorous Gasteropods, 
with the exception of Purpura tetragona—which by the way has an 
extremely thin calcite layer; there is, however, at Jermyn Street a 
bored specimen of the Purpura lapillus. The calcite shells seem to 
enjoy a like immunity from the operations of boring Annelids, but 
here again I have seen an exception in the case of a Pecten in which 
an abortive attempt had been made to excavate a crypt. 
I understand that Purpura lapillus and Murex erinaceus do a great 
deal of damage to our Whitstable oyster beds by boring the young 
shells. The modern “ Natives,” however, have very thin shells as 
’ compared with the crag O. edulis. 
Certain species of adnate Polyzoa (e.g. Lepralia puncturata and 
Hippothoa abstersa) frequently excavate a little hollow at the back 
of each cell when encrusting aragonite shells, but I have never seen 
a calcite shell similarly hollowed. Cliona borings are abundant in 
the Crag shells, whether of aragonite or calcite. 
I may remark in conclusion that the consolidation of the Coralline 
Crag and the dissolution of the aragonite shells appears to have 
taken place previously to the deposition of the Red Crag, or at any 
rate of the Middle part of it, as I have found a fragment of Coralline 
Crag with shells and casts in the coprolite diggings at Boyton. 
