58 W. H. RmUesfon—On the Yorkshire Oolites. 



Thus it is evident that, on many horizons, and in countries far 

 distant, these two sections seem to have been ranged side by side 

 wherever the group was at all numerous, and although this fact may 

 be lost sight of in a fog of synonyms, and of specific names created 

 for small differences, it will be surely recognized by those who 

 regard the whole system of species-making as one that requires 

 modification, if we are to arrive at a correct understanding of the 

 life history of the past. 



24. — Cerithium gemmatum, Morris and Lycett, 1850. Plate ITT. 



Fig. 9. 



1850. Cerithium gemmatum, Morris and Lycett, Great Ool. Moll. p. 115, pi. xv. 



fig. 6. 

 1875. Ibid. Ibid. Phillips's G.T. 3rd ed. p. 258. 



BihliograpJiy, etc. — The authors describe their specimen as from 

 the " Great Oolite near Scarborough." I have not traced the type, 

 but the specimen now figured resembles it very fairly. The follow- 

 ing is the original description. '' Shell small, turrited ; volutions 

 rather convex, encircled with 5 rows of nodules ; nodules ovate, 

 about 24 in a volution ; the rows of nodules are slightly curved, and 

 the last volution has from 7 to 9 rows. 



The little nodules are regular, oval, their longer diameter being 

 in the axis of the shell, and they are distant from each other about 

 their own diameter ; the number of volutions are but few, apparently 

 not more than 7. Length 7 lines, transverse diameter 2 lines." 



Description. — Specimen from the Scarborough Limestone (zone 3). 

 Bean Collection, British Museum. 



Length 15 millimetres. 



Width 4f ,, 



Spiral angle 20°. 



Except as regards the number of whorls, the original description, 

 quoted above, would do very fairly. In this one 8 whorls can be 

 counted, and at least 3 more must have existed on the spire, making 

 11 in all. The little oval granules of the upper spiral in each 

 whorl are somewhat stouter than the rest : the whorls are very 

 regularly convex, and the body-whorl is decidedly full : the base 

 is ornamented with spiral bands, of which the two uppermost are 

 granulated, the granules being drawn out spirally, and less deeply 

 cut out than those of the spire. The body-whorl shows 6 spirals on 

 the flank (Fig. 9a). 



Relations and Distribution. — This very elegant little Cerithium is 

 probably remotely connected with the muricatum-gvoxx^, from which 

 it is separated by the more convex character of the whorl, by the 

 excessive closeness of the longitudinals, and by the fact of the 

 nodes or granules being drawn out axially (longitudinally) and not 

 ispirally ; which latter seems an important difference, since in all the 

 varieties referred to the muricatum-g^row^, which are figured in the 

 accompanying Plate, the nodes or granules are drawn out spirally. 

 The beaded character of the granulations is partly due, I suspect, to 

 the effect of the marly matrix, and hence this point of difference need 

 not be insisted on too strongly. 



