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E. ETHEEIDGE ON A TEIGONIA FEOM THE 



17. On a New Species of Teigonia from the Puebeck Beds of the 

 Yale of Waedoue. By E. Etheeidge, Esq., E.E.S., Pres. G.S. 

 With a Note on the Strata, by the Ret. W. E. Andrews, 

 M.A. (Eead December 15, 1880). 



Eaelt in this year the Eev. W. E. Andrews, of TefFont Eectory, 

 near Salisbury, placed in my hands what at first sight appeared to- 

 be a new species of Trigonia from the Purbeck rocks in the Yale of 

 Wardour. This new species was found by Mr. Andrews in the rail- 

 way-cutting one mile west of Dinton Station in the Yale of "Wardour ; 

 and its geological or stratigraphical horizon is the " Cinderbed " so 

 well known in the several sections in the Isle of Purbeck and else- 

 where. This bed is here composed of hard grey marl and pale 

 brown soft limestones, variable in their proportions. Ostrea distorta 

 and casts of Trigonia abound in this Cinderbed, which here measures 

 about 2 ft. 6 in. in thickness. The section accompanying this 

 paper (fig. 2, p. 252) was constructed by Mr. Andrews, and most 

 correctly represents the succession of the Lower and Middle Pur- 

 becks at the spot in the vale whence the new Trigonia came. It 

 was from this marine "Cinderbed " at Durlston Bay that Hemicidaris 

 pnrbecJcensis, Eorbes, was obtained, associated with Ostrea distorta, 

 a Trigonia like T. gibbosa, Cardium Gibbsii, Perna sp., and remains 

 of fish. No other locality or section of the Dorsetshire Purbecks 

 has yielded the above. There cannot be any doubt that this Tri- 

 gonia is not T. gibbosa. The Eev. 0. Eisher obtained Trigonia gib- 

 bosa (?) from the middle Cinderbed of Eovant, "Wilts; and the Eev. Mr. 

 Andrews has obtained four other specimens of the same species from 

 his immediate area ; so that the genus is well represented in the 

 Middle Purbeck of the Yale of Wardour. The Lower Purbeck beds 

 of the vale lie below the datum of the railway and the level at 

 which many of the quarries are worked, the " Juxeat " beds being 

 about the lowest seen. The beds exposed in the railway-section near 

 TefFont include the base of the Wealden, all the Middle Purbecks of 

 the Yale of Wardour, and the top of the Lower Purbecks. The middle 

 group here is about the same thickness as the beds in the Isle of 

 Purbeck ; those at Eidgway Hill and Mewps Bay are about 50 ft. ; 

 and at Worborrow Bay the middle series measures 90 ft., and at 

 Durlston Bay 150 ft. There is no Upper Purbeck in the area 

 under observation ; the hard marl with eroded surface is the highest 

 member of the Middle Purbeck, the succeeding 17 ft. being probably 

 Hastings Sand at the base of the Wealden. 



Description. 

 Section Glabrae. 

 Teigonia densinoda, Ether. (Eig. 1.) 



Shell greatly elongated or lengthened posteally, the anteal or 



