INTRODUCTION. 13 



Passing upwards we at once take leave of the numerous Trigoniae that characterise 

 the Lower Oolites ; for, although some species occur in immense abundance at certain 

 localities, the number of Jurassic species in any one stage are comparatively few, and in 

 the Middle and Upper Oolites, from the Kelloway Rock to the Portland Oolite inclusive, 

 only twenty-five additional species have been procured. The Oxfordian Trigoniae are the 

 following : T. paucicosta, T. denticulata, T. complanata, T. Mupellensis, T. elongata, T. 

 clavettata, T. irregularis, T. triquetra, T. corattina, T. composita, T. perlata, T. monilifera. 



The Portlandian series, including Kimmeridge Clay, Portland Sand, and Portland 

 Oolite, have T. irregularis, T. Juddiana, T. Pellati, T. muricala T. Carrei, T. gibbosa, T. 

 Damoniana, T. Micheloti, T. Manselli, T. incurva, T. tenui-texta, T. Woodioardi, T. Voltzii. 



In the Cretaceous system of rocks, the species of the Neocomian formation are T. 

 nodosa, T. caudata, T. carinata, T. ornata, T. spinosa, T. Picteti, T. Pyrrha, T. Orbig- 

 nyana, T. Etheridgei, T. ingens. 



The Gault has T. Fittoni. 



In the Upper Green Sand are T. tenuisulcata, T. Archiaciana, T. excentrica, T. 

 spectabilis, T. crenulata, ? T. aliformis, T. doedalea, T. abrupta, T. ornata, T. Cunningtoni. 



The author has much pleasure in recording his grateful acknowledgments for the 

 valuable and varied assistance which he has received in the execution of his task. To Sir 

 Roderick Murchison, Director General of the National Geological Survey, his thanks are 

 due for the liberality which made the resources of the Museum of Practical Geology 

 available for his use. The permission thus accorded has been rendered more especially 

 valuable by the cordial co-operation of Mr. Etheridge in carrying out the wishes of 

 the author, and also in procuring the loan of other valuable specimens. Mr. J. W. Judd, 

 lately an officer of the Survey, has also freely and repeatedly communicated information 

 respecting the range and distribution of the species throughout the district of the Midland 

 Counties, which he is so well qualified to afford. Similar kindness and co-operation on 

 the part of Mr. Henry Woodward, of the British Museum, has enabled the author to 

 utilize to the fullest extent the great resources of that collection, and more especially in 

 the comparison and study of the numerous and splendid foreign examples of Trigonia 

 which form so conspicuous a feature in its fossil conchology. 



Mr. Cunnington, of Devizes, whose collection so well exemplifies the fossil faunas of 

 the Upper Jurassic and Cretaceous rocks of that part of England, kindly forwarded every- 

 thing calculated to illustrate that portion of the subject. The following gentlemen have 

 also afforded material assistance either by the gift or the loan of specimens : — Rev. P. B. 

 Brodie, of Rowington ; Rev. J. E. Cross, of Appleby, Lincolnshire ; Professor J. Buckman ; 

 Mr. J. Leckenby, of Scarborough ; Mr. P. Hawkridge, of the same place ; Mr. Beesley, of 

 Banbury ; Rev. C. L. Smith, of Canfield, Essex ; Mr. J. Walker, of York ; Mr. E. Witchell, 

 of Stroud ; Dr. T. Wright, of Cheltenham ; Mr. R. Tate, of Camberwell ; Mr. Samuel 

 Sharp, of Northampton ; Mr. Mansell, of Blandford, Dorset ; also Dr. J. Lowe, of Lynn. 



