SUPPLEMENT. 7 



In Oxfordshire, at Hook Norton^ and Rolhiglit Heath, which have produced this 

 species less rarely, these varietal features are more strongly developed, and specimens 

 have greater differences of aspect. Eor a better knowledge of these, and for the 

 comparison of instructive illustrative specimens, I am much indebted to Mr. E. A. Walford, 

 of Banbury, who forwarded to me his collection from the Inferior Oolite of Oxfordshire, 

 together with that of another industrious collector, Mr. J. Windoes, of Chipping Norton, 

 in the same County. The notes which Mr. Walford has supplied to me describing the 

 strata of Hook Norton and their fossil contents evince discriminative ability and minute 

 observation ; they entitle him to my sincere thanks. 



The description of Trigonia signata, Ag., var. Zietenii, given at page 29, is sufficient 

 to render further remarks unnecessary ; they may, however, be supplemented by the note 

 upon Trigonia ingens, page 207, comparing the latter with the Inferior-Oolite shell. So 

 considerable is the zoological affinity between these two forms that I have seen experienced 

 observers take up the Neocomian form in the full belief that they were handling the shell 

 of the Inferior Oolite. No doubt the distinctive differences indicated at page 207 are 

 constant and reliable ; but these are of such small importance in a zoological point of 

 view, that it is difficult to escape the conviction that in the Inferior-Oolite shell Trigonia 

 signata, var. Zietenii^ we see the precursor or progenitor of the Neocomian T. ingens, 

 however great may be the stratigraphical hiatus separating the two forms. I have therefore 

 ■deemed it desirable to figure two of the Oxfordshire forms which exhibit variations in 

 the surface ornaments, and also one additional Yorkshire example which has none of these 

 individual peculiarities. Trigon. SuppL, Plate I, figs. 10, 17, represent two little imma- 

 ture forms which appear to be examples of the same variety in a very young state ; one of 

 these (fig. 17) is from the Upper Trigonia-grit of Rodborough Hill, supplied by my 

 friend Mr. Witchell ; the other (fig. 10), of nearly similar dimensions, was collected by 

 Mr. Windoes in one of the lower beds of the formation in Oxfordshire; these two 

 specimens have a distinct plain marginal carina and tuberculated inner carina even as 

 far as the apex, the costae then become slightly tuberculated at the third row, and the 

 general ornamentation of the valve is thence established. 



The Oxfordshire collections forwarded to me by Mr. Stutterd, by Mr. Walford, and 

 Mr. Windoes, are also especially interesting, as they exhibit three other well-marked 



^ The following general section of the strata at Hook Norton has been supplied to me by Mr. 

 E, A. Walford : 



Feet. luf 



Upper Lias Leda ovum beds (at bottom) 



A. Sand and blue hearted limestone .... 



B. Flaggy limestone, very sandy .... 



C. Limestone courses, divided by sand .... 



D. Sands, clays, and thin courses of limestone, with plant remains 



E. Sand with oysters, pectens, bored limestone, and sandy whitish lime- 



stone (Rollright Grits) ..... 



2 



3 



1 



6 



4 



8 



[7 







