260 Mr. J. Lycctt on some new species 0/ Trigonia 



different, T. angulata being much more elongated, and the urn- 

 bones more recurved ; the surface ornaments of the shells like- 

 wise differ; those of T. angulata are remarkably constant and 

 invariable. 



T. undulata has not been recognized in the Oolites of England ; 

 on the other hand, T. angulata has not been discovered upon the 

 continent. T. angulata has occurred at many localities in the 

 Cotteswolds, both in the middle and upper portions of the Infe- 

 rior Oolite, but it is rare. The imperfect specimen of T. angu- 

 lata from Little Sodbury, which is given in the two lower figures 

 of table 87 of the ' Mineral Conchology ' as T, clavellata, has 

 been the source of much confusion to subsequent observers, and 

 has led them to catalogue clavellated specimens (usually imper- 

 fectly exposed) as Trigonia clavellata ; but the figure in the same 

 work of T. angulata is so characteristic, that it may be relied 

 upon when the shell itself cannot be obtained for comparison. 



Trigonia duplicata, Sow. 

 Trigonia duplicata, Sow. Min. Con. tab. 237. figs. 4, 5. 



Shell slightly rostrated, area narrow, carina? two in each valve, 

 small, distinct ; costse narrow, serrated, the first few concentric, 

 the others directed downwards, for the most part bifurcated and 

 slightly waved. Should the T. Proserpina of D'Orbigny prove 

 to be distinct from this species, it must possess peculiarities 

 which are not alluded to in his ' Prodrome de Paleontologie/ 

 where the brief description given agrees with T. duplicata. M. 

 Agassiz (probably from an imperfect knowledge of the species) 

 has placed T. duplicata with the Scabrce, but the very distinct 

 marginal carina and the area destitute of transverse costse clearly 

 remove it from that section, which first appeared with the species 

 of the lower greensand. 



T. duplicata occurs in the upper division of the Inferior Oolite 

 in the Cotteswolds, where the external impressions are not un- 

 common, but the shell itself is rare ; it has also been found in 

 the Great Oolite of Minchinhampton. 



Trigonia Phillipsi var. 



Trigonia Phillipsi, Mor. & Lye. Gr. Ool. Monogr. 1853, tab. G. fig. 1 . 

 p. 62. 



Shell ovately trigonal ; umbones submedian, obtuse, scarcely 

 recurved, anterior border rounded, posterior border short, trun- 

 cated; marginal and inner carinse delicate, tuberculated and 

 small ; area narrow, flattened, striated, divided in its middle by 

 an oblique furrow ; sides of the valves with densely arranged, 

 elevated, concentric, and finely indented or tuberculated costae. 



