J. F. BLAKE ON THE KIMMERIDGE CLAY OF ENGLAND. 225 



and 4 longitudinal, and another with 16 transverse and 6 longi- 

 tudinal, in which case they appear like distinct species; but the 

 union of 16 transverse and 4 longitudinal, or of 13 and 6 respec- 

 tively, warns us they are one variable species. 



Goldfuss's Cerithium costellatum and muricato-costatum so exactly 

 represent the two extreme varieties of this, that it is only their 

 coming from different horizons from each other and from this that 

 makes me assign a new name ; if any difference is to be found, it 

 is that costellatum has broader whorls, and that in muricato-costa- 

 tum the horizontal portion below the suture is broader. C. nodoso- 

 costatum (Miinst.) has its spiral angle larger, making it a more 

 inflated shell. 



Yery common and characteristic of Lower Kimmeridge in Lin- 

 colnshire and Dorsetshire. 



Cerithium crebrum, n. sp. PL XII. fig. 14. 



In general shape this is very similar to the last, perhaps rather 

 more acute, but differs in the ornamentation, and is itself variable. 

 The spaces between the whorls are more excavated ; and the hori- 

 zontal portion has often fine longitudinal ribs. The transverse 

 ribs are more numerous, being 18 in number. The longitudinal 

 ribs are irregular, not of equal strength, not more than four of 

 full strength, variable in the extent to which they influence the 

 transverse ribs, in some making almost tubercles ; the top row always 

 sharp and prominent. Length j inch. 



This is, no doubt, the English representative of C. limceforme 

 (Bom.). Buvignier (Geol. de la IVfeuse, pi. xxviii. fig. 3) figures a 

 shell under that name very like ours, but with each whorl more 

 convex and less separated from the next ; but the original, as figured 

 by Bomer, is much more distinct. 



Less common than the last, in the Lower Kimmeridge of Lincoln- 

 shire. 



Cerithium multiplicatum, n. sp. PI. XII. fig. 15. 



This has also a similar appearance to the last two ; in fact it is 

 a step beyond the variety of O. forticostatum with most longi- 

 tudinal ribs. In this the transverse ribs are most elevated at the 

 top (as in JRostellaria rasenensis), where they end abruptly ; the 

 longitudinal ribs are about 12 in number, very fine, and scarcely 

 influence the transverse ones, of which there are 12 ; the underpart 

 of the last whorl has stronger longitudinal ribs, with transverse ones 

 slightly twice bent, not corresponding with those on the side. This 

 is, no doubt, the representative of G. septemplicatum (Bom.) ; but it 

 differs from it in having more longitudinal ribs and stronger trans- 

 verse ones. Length 1 inch. 



This represents in Wiltshire, where it is common in the Lower 

 Kimmeridge, the C. forticostatum of Lincolnshire. 



Tornatella secalina (Buv.), ' Geol. de la Meuse,' pi. xxiii. fig. 34. 

 I have great doubt in referring a single specimen to this 



