48 Obituary— Mr. Searks V. Wood. 



International Committee of Geological Nomenclature, in 1883, a 

 majdrity voted in favour of the limit between the two divisions being 

 drawn below the Callovian. 



The lines of division to which geologists generallj'^ attach impor- 

 tance are breaks in the sequence, shown by unconformity or by 

 changes in the sedimentation. Mr. Jukes-Browne very naturally 

 wishes, as most other English geologists have done, to draw a limit 

 where the calcareous deposits of the Middle Jurassics cease in 

 England, and the argillaceous beds of the Upper Jurassics come in. 

 Such a division, however well marked locally, has no general value, 

 the change being confined to but a small portion of the earth's 

 surface. 



My reason for classing the Oxford Clay as Middle Jurassic is that, 

 by so doing, the series or primary subdivisions of the system are 

 more nearly equal in value. I take four fairl}^ representative modern 

 classifications, those of Eenevier (1873-74), Meyer-Eymar (1881), 

 Geikie (1882), and De Lapparent (1883). Under Renevier's arrange- 

 ment, if the Oxford Clay (and Callovian) be classed in the higher 

 series, the upper subdivision would contain 3 " systemes " comprising 

 9 " etages," the middle 1 " systeme," and 4 " stages. By Meyer- 

 Eymar's arrangement, the upper would contain 4 etages consisting of 

 12 sous-etoges, (or if the Purbeck, classed by Meyer-Eymar in the 

 Lower Cretaceous series, be added, as it would by most geologists, 

 5 and 14), the middle 3 etages, consisting of 8 sous-etages. In Mr. 

 Geikie's classification two divisions would be assigned to the Upper 

 Jurassic, one only to the Middle, whilst in De Lap})arent's 4 etages 

 with 11 sous-etages would belong to the former, and only 2 etages 

 with 4 sous-etages to the latter. If on the other hand the Oxfordian 

 and Callovian are classed with the Middle Jurassic, the difference in 

 palfBontological importance between that and the upper subdivision, 

 under any of the systems of classification quoted, would be small. 



I carefully abstained from proposing new names, as so many have 

 already been given to various Jurassic subdivisions. Those proposed 

 by Mr. Jukes-Browne have certainly an advantage, on the score of 

 euphony, over the terms Malm and Dogger, but the latter are widely 

 known. 



I must deprecate the use of the term " stage," in the sense in 

 which it is employed by Mr. Jukes-Browne. An English term is 

 urgently required as the equivalent of the French etage. This is 

 never used for divisions of the rank of upper, middle or lower 

 Jurassic, but always for smaller terms such as Purbeck, Portland, 

 Kimmeridge, etc. If " stage " is restricted to the same meaning, the 

 term will be far more useful than if employed as loosely as, for 

 instance, "group" and "series" have been. 



November Idth, 1884. W. T. Blanfohd. 



We regret to announce the death of Mr. Searles V. Wood, F.G.S., 

 Treasurer of the Palasontographical Society, on Sunday the 14th 

 December, 1884, at his residence, Beacon Hill House, Martlesham, 

 Woodbridge, after an illness of nine years duration. 



