202 W. JET. Hudleston — On the Yorkshire Oolites. 



(Fig. 12). Specimen from the Kelloway Kock (zone 5), Scar- 

 borough. Leckenby Collection. 



In this case the proportions are practically the same as in the 

 px'evious cases, but the state of preservation is one of unusual excel- 

 lence. The specimen has been obtained from the calciferous grit, 

 or "chert-bed." ^ It displays an ornamentation consisting of flat 

 ribands divided by narrow and shallow sulci (see enlargement). 

 This is probably a faithful picture of the original surface of the 

 shell, such as may be seen in so many existing Naticas. Another 

 stage of fossilization would probably reveal that sort of decussation 

 of these lines of growth with spiral lines which has so large a share 

 in producing punctate structure. The eye of faith, aided by a power- 

 ful magnifier, might perchance see it here, but neither the artist nor 

 myself have been able to do so. Yet it may exist and only requires 

 a developer to bring out the picture. 



Belations and Distribution. — Bean, as we know, had no doubt about 

 the fossils from the Dogger and the Cornbrash being practically the 

 same species. This form is perhaps the commonest species referred 

 to Natica in the Dogger, and is far from rare in the 2nd and 3rd 

 zones, though there the punctate character is not well shown owing 

 to the status of the fossils. A species so plentiful and with such a 

 large vertical range must needs be tolerably abundant in the Bajocian 

 beds of other regions. Partly for this reason I cannot but think 

 that N. Bajocensis, so abundant at Burton Bradstock and elsewhere, 

 is the representative, at any rate of the variety of N. punctura, so 

 common in the three zones of the Inferior Oolite of Yorkshire. The 

 general contour of the shell and of the whoids is the same. More- 

 over, the proportions, which I take to be by far the most important 

 element in the diagnosis of these unornamented shells, correspond 

 almost exactly with those given by D'Orbigny (op. cit. p. 189). 

 There remains the difficulty of the punctate structure. The typical 

 N. Bajocensis is not described by the author as punctate, whereas the 

 Dogger shells always are, though not as a rule from the two other 

 zones of the Inferior Oolite of Yorkshire. I believe this punctate 

 condition to be very much a matter of status, being developed under 

 certain circumstances and in certain kinds of matrix, and that its 

 presence or absence is not always to be regarded as a crucial test of 

 the relations of a fossil. 



Should it be deemed desirable to sepat'ate the Inferior Oolite form 

 from that of the " Cornbrash " and " Kelloway," the former would 

 become N. Bajocensis, D'Orb., the latter remaining as before. 



9. — Natica Calypso, D'Orbigny, var. tenths. Plate V. Fig. 13. 

 1852. Watiea Calypso, D'Orb., T. J. p. 202, pi. 222, figs. 9, 10. 



Description. — Specimen from the Lower Calcareous Grit (zone 7), 

 Cay ton Bay. Leckenby Collection. 



Length 15-5 mm. 



Width 8-5 ,, 



Eatio of body-whorl to entire shell 61 : 100. 



Spiral angle 50^ 



1 See Introduction. 



