1859. j WRIGHT INFERIOR OOLITE. 45 



" I have been to Rodborough Fort today, Nov. 13, 1858, to take 

 more exact observations on the bed with Gryphites ; and the following 

 is the result. Your account of the Trigonia-grit is sufficiently cor- 

 rect ; and it is very remarkable how small at that place is the thick- 

 ness of the rags between the Trigonia-grit and the Freestone or 

 bored beds. At the eastern end of the quarries they are only two 

 feet, and the separation into two beds is not very well defined ; but 

 towards the western side, that is, next to the Fort, it is clearly 

 divided into two beds, which have an aggregate thickness of at least 

 three feet. The upper portion is much harder than the lower, and 

 is more siliceous, becoming at intervals concretionary, and abounding 

 throughout its mass with the valves of Gryphites ; in smaller num- 

 bers are other shells. As the bed is generally very- hard, it is difficult 

 to obtain anything like an accurate list of them ; but I imagine there 

 are on the whole a goodly list of Testacea, together with a few corals. 



" The Gryphites are found in the basement-bed of the rags, almost 

 down to the freestone. The prevailing character of the basement-bed 

 is its argillaceous dark-grey colour ; but there is much variability in 

 its hardness and colour in its course through the long range of 

 quarries. Upon the whole, I cannot see that the fossils of the 

 Gryphite-stratum at this place can be dissociated from those of the 

 crowded stratum next below ; but I can quite understand that, 

 where the rock has greater mass, the superposition of the fossils 

 may be more distinctly marked, and that the Gryphite-berl may be 

 more clearly separated* from that beneath it. I fully remember that 

 in a quarry upon the northern side of the valley, one and a half or 

 two miles X.E. of Stroud, the Gr>/pJuea> occur in two distinct zones, 

 with about three feet of rock between them." 



Under the name " Pholadomya-grit," Dr. Lycett designates the 

 uppermost beds of the upper Trigonia-grit, in which he has found 

 the following species : — 



Ilomomya gibbosa. Sow. 

 Pholadomya Heraulti, Ay. 



Dewalquei, Li/c. 



Ceromya plicate. Bow. 



striata. Sow. 



Terobratula ghihata, Bow. 



Terebratula carinate, Lamk. 



Rhyni'honclla angulata, 8otO. 



spinosa, Scnloth. 



( l\ peas Plotii, K/i in. 

 Holcetypns depressiiH, Lamk. 



Fbssils of A. Upper Trigonia-grit. 



Ammonites Parkinsoni, Sow. 



liartaiuii, if Orb. 



Trigonia ooetete, Bow. 



V-eostata, Lye. 



duplicate, Sow. 



signata, Ag. 



pro i lu. ia. Lye.* 



I ►pia nmilis, Sow. 

 Oardium Buokmani, Lyo. 

 Dnioardiom iIiiiiuwhiiiii. Phil. 

 Qoenstodtia langate, I'hil. 



Marrodon ] 1 irsoiu ■ t i ~ i — . iFArcfi. 



TrichiteB andalataa / 



I'.xt.'ll drill i.-Ml*. /'//,/. 



* This note on Trigonia prodlteta has DMO kindly (Mininuiiiiai.il l>v Mi 

 author: — 



Trigonia pndueta, Dyoett The hard app*T Trigtmia-nrit at Kodlwrough 

 Hill baa produced, rarelT, an elongated Trigonia allied t<» TTangutata, Bow., bed 

 distinguished i>v the following ohanoten i It i* mnofa more produoed and gtte- 



