226 Mr. J. Lycett on some new species of Trigoiiia 



less strongly felt ujjou a contemplation of the altered, and in 

 some measure degenerated characters of the living species. 

 But if the attributes claimed for the genus at the fera which im- 

 mediately precedes the extinction of the Cretaceous species are 

 well founded, it will, I think, a])pear equally evident that at its 

 primal fera in the earlier portion of the Oolitic system the genus 

 had already acquired that prominence amongst the Testacea 

 which Von Buch has so vividly described, and that the forms, 

 dimensions, and ornamentations of the species were scarcely less 

 characteristic and vai'ied. Upon numbering the entire recorded 

 species of Triffonia, it will be found that about two-thirds arc 

 proper to the Oolitic rocks ; and although some little aljatcment 

 must be made, for instances in which young individuals, varieties, 

 or mere casts have been erected into distinct species, the predo- 

 minance of Oolitic forms will remain, inasmuch as the Cretaceous 

 species are not exempt from similar errors of augmentation. 

 The inadequate manner in which the Inferior Oolite Trigonue 

 have been illustrated, will appear, when it is stated that of the 

 sixteen species recorded in the present paper, four only will be 

 found illustrated in the range of English literatui-e ; a fifth occurs 

 in the * Memoire sur les Trigonees ' of Agassiz, and two others 

 are on the eve of being published in a ' Monograph of the 

 Palasontographical Society,' leaving upwards of nine species un- 

 figured, a number which will be admitted to be remarkable when 

 we remember that SI. D'Orbigny has only enumei'ated seven in 

 his ' Prodrome dc Paleontologie ' for the Terrain Bajocien of the 

 whole of France, and M. Agassiz twelve from the entire lower 

 Oolite rocks of Germany, France and Switzerland. The present 

 examination of Inferior Oolite species has been suggested by the 

 frequent occurrence in collections of Trigonia costata, clavellata 

 and angulata, or of shells bearing those names, pertaining to 

 nearly the entire series of the Oolitic rocks of England and 

 France ; the aspect of these shells is so varied and dissimilar, 

 that they agree with each other and with the tyj>ical forms of 

 those species only, inasmuch as the first portion is costated, the 

 second clavellated, and the remainder have their costse bent to 

 form an angle. 



M. Agassiz, in his valuable memoir on Trigonia, arranged the 

 species into upwards of eight sections, some of which appear to 

 be separated by distinctions so transitive that it is scarcely pos- 

 sible to apply them to a large number of specimens, except in 

 an arbitrary and unsatisfactory manner ; a more simple arrange- 

 ment here proposed will probably answer every practical purpose, 

 and has at least the advantage of being more readily understood 

 and applied ; the genus will thus form six sections, of which one, 

 the Pectine?, is recent only; the five fossil sections consisting of 



