THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[SECOND SERIES.] 

 No. 70. OCTOBER 1853. 



XXIIT. — On some new species of Tvigonia from the Inferior Oolite 

 of the Cotteswolds, with preliminary Remarks upon that Genus. 

 By John Lycett, Esq.* 



[With a Plate.] 



" Not only by their numbers, but still more by the richness of theii* spe- 

 cific divisions, by the peculiar prominence of individualization, do the 

 species of the remarkable genus Trigonia attain their maximum point in 

 the lower chalk." — L. von Buch, Betrachtungen uber die Verbreitung und 

 die Grenzen der Kreide Bildungen. Bonn, 1849. 



Trigonia and Pholadomya are the two organic forms which 

 pre-eminently serve to impress a distinctive character upon the 

 Testacea of the Oolite rocks in whatever country they ai-e dis- 

 covered, and accordingly from the time when fossil shells were 

 regarded as mere freaks of nature, we find that authors depicted 

 their Hippocephaloides and Bucardites. But conspicuous as is 

 the position which Trigonia holds throughout the Oolites, the 

 quotation above chosen, and the passages which immediately 

 follow, ai*e not the less true and worthy of notice ; they evince 

 the strong impression made upon the mind of a distinguished 

 and veteran palaeontologist by the remarkable prominence which 

 the genus Trigonia holds amongst the Cretaceous Conchifera, 

 both in its numbers and world-wide distribution, a prominence 

 which appears not the less remarkable when we remember that 

 the leading sectional oolitic forms of the genus had already 

 nearly disappeared, and that a little higher in the series even the 

 cretaceous forms exhibit a rapid diminution, until in the upper 

 chalk a trifling remnant alone remains to indicate the forth- 

 coming extinction of the fossil T-igonice, a loss which is not the 



♦ Read to the Cotteswold NatvuaUsts' Club, July 19, 1853. 

 Ann. fif Mag. N. Hist. Ser, 2. Vol. xii. 16 



