﻿182 



SUPPLEMENT TO THE CRAG MOLLUSCA. 



Cancellaria umbilicaris? Brocchi. Addendum Plate, fig. 10. 



Voluta umbilicaris, Broc. Conch. Foss. Subap., vol. ii, p. 312, tab. iii, figs. 10, 11. 

 Cancellaria — Bellardi. Foss. de Piemont., p. 36, tav. iv, figs. 17, 18. 



Spec. Char. " C. Testa ventricosa, anfractibus, scalar if ormibus, canaliculatis, lonqitu- 

 dinaliter costata, prof uncle transversim sulcata, sulcis subimbricatis crispis, umbilico patent- 

 issimo, usque ad apicem spira pervio." — Broc. 



Locality. Red Crag, Waldringfield. 



The Rev. H. Canham has sent to me for representation a very perfect specimen which he 

 has obtained from the Red Crag at Waldringfield, and this I have referred as above, with 

 some doubt, as it does not strictly conform to any of the figures representing the foreign 

 specimens under the name of C. umbilicaris. Our shell may probably be a dwarf 

 variety of this species, with a depressed spire. 



Our present specimen, there can be no doubt, is merely present as a derivative in the 

 Red Crag, but whether it be derived from the Coralline Crag or from some older bed, 

 there are not at present the means of judging. 



I have from the Cor. Crag a very imperfect specimen belonging to this genus, 

 which is distinct from any other that I have previously described, but it is too imperfect 

 for representation. It somewhat resembles C. elongata, Nyst. 



Cancellaria subspinulosa, Supplement ' Crag Moll.,' PI. VI, fig. 10, may possibly be 

 the young C. lyrata, Broc, but better specimens than I possess will be required for its 

 determination. 



Pyramidella l^evinscula, S. Wood. Crag Moll., vol. i, p. 77, Tab. IX, fig. 2. 



Supplement, p. 57. 



Mr. Jeffreys has kindly sent to me for examination some recent specimens obtained in 

 the Mediterranean, and from his deep sea dredgings, which he considers identical with 

 my Crag shell. On comparison I find the recent specimens more conical in shape, and 

 more resembling P. conulus, Speyer ('Die Conch, der Cass. Tertiar.,' Tab. XXV, fig. 1. 

 In his letter Mr. Jeffreys says, " There is some difference between the Porcupine and 

 Crag shells, which I consider varietal only, consequent on some alteration in the conditions 

 of habitat. I make some allowance for the great lapse of time and subsequent change of 

 form." The lapse of time and alteration of conditions are, I believe, the main causes 

 operating to produce new species, and inasmuch as the more our knowledge of recent 

 find fossil forms extend, the greater will be the perplexity among palaeontologists where 

 to draw a line of specific distinction, and the more will they be driven for classification 



