154 SUPPLEMENTARY INDEX TO VOL. IV. 



From what Mr. James D. C. Sowerby, has lately stated to me, I see 

 reason also to think, that a small miconformable patch of these anomalous 

 Strata (which I shall continue to call the Cowes Rock, because there, my 

 departed Friend Mr. Sowerby first noticed and enriched his Cabinet, 

 with the peculiar Shells of these strata) rests upon theedges of the London 

 Deep- Well Strata, in the vicinity of Charlton near Woolwich: also, since 

 compiling the stratigraphical Index to your third Volume, I have perceived, 

 that the patch or patches of Crag-Marl in Essex, Suffolk and Norfolk, by 

 lying upon the edges of the London Clay, and of its deep- well Strata, 

 shews, that the Crag must be referred to comparatively modern, uncon- 

 formable strata ; but whether of the same, or a more antient or more 

 recent era, than those of Paris, and the Isle of Wight &c. above men- 

 tioned, I pretend not to say, but for the present shall continue to dis- 

 tinguish them, and place the Crag the lowest. 



I have been much pleased to see Messrs. Conybeare and Phillips* 

 introducing a set of Terms, for denominating the Orders or greater 

 Divisions of the British Strata, five in number, v\hich, if generally 

 adopted, would free us from the use of those mischievously theoretic 

 terms and distinctions, Primary, Transition, Fidtz, independant Coal, Fl'dtz- 

 trap. Secondary, Sec and rid us of the many futile disputes, to which they 

 bavegivenrise, and which they seem calculated to perpetuate in Geological 

 writings : the Or-ders of Mr. Conybeare are accordingly introduced in 

 t!ie following Index. 



As f.ir as I could, I have availed myself of the excellent and cheap 

 County Geological Maps of Mr. Smith (which are publishing by Mr. Caiy, 

 and sold separate) and of liis Geological Table and Sections, and his other 

 I'ublications, in ascertaining the stratigraphical places, from the Geo- 

 graphical places;, of the several Shells described in this Volume; and have 

 little attended to. many corrections which have, as appears to me, been 

 rashly offered, and continue to be repeated or varied, almost monthly, 

 !is to the super-position or succession, and the Names, of some of the 

 English Strata, and a* to their courses across, or their detached appear- 

 ances, in different parts of the country. 



'llie number of Species of Shells named in the present Volume is 148, 

 besides 4 varieties distinguished by Mr. Sowerby by /3, but which never- 

 theless belong, to the same strata as their relative Shells marked a ; in 

 addition to which, I have been induced to propose the separation of 12 

 other varieties, partly on account of their belonging to (/J/ferfw< (S^rafa; 

 Making thus 160 Species (or varieties) belonging as I believe to dis- 

 tinct Strata, described in the present Volume. 



In the 4(ith, 52nd and ."iyth Volumes of the " Philosophical Magazine," 

 Dr. Tilloch has done me the favor to insert geographical Indexes, to the 

 three former Velumes ot your Min. Conch, and in a few days I intend 

 to forward to him, a similar Index for the present Volume; which will 

 describe the local situation and the place in the Strata, of each Shell 

 figured herein. 



I beg to add 

 A continuation of, and additions to the TABLES in pages 2i3 of Vol. If. 

 and 188 o/ Vol. HI ; paiticularizing such species of SHELLS, as are in 

 the four Volmnes of this Work, and in. Mr. Smith's two unfinished Works 

 vH Fossil Shells, referred to more than one STRATUM; In the Index 

 which follows, these muHistratular SHELLS are distinguished by the 

 Greek Letters a and Q, unless otherwise mentioned below. 



Genera. Species. No. of Species, Vol. Page, 

 or St rat. Var. 



Ammonites Grenoughi 2 II 71 



jugosa 2 I 207 



Parkinsoni, a, /3 & 7 3 IV 182 



Dentalium cyliudricum 2 I 178 



* In their " Outlines of the Geology of England and Wales," p. vi. &Co 



