38 BRITISH FOSSIL TRIGONE. 



Trigonia Phillipsi, Mor. and Lye. Plate VI, figs. 3, 4. 



Trigonia striata, Agassiz. Trigonies, 1840, pi. iv, fig. 12 (not figs. 10, 11). 



Phillipsi, Mor. and Lye. Pal. Soc. Gr. Ool. Monog., 1853, tab. 6, 



fig. 1, p. G2. 

 — Morris. Catal., 1854, p. 228. 



Shell sub-ovate, convex ; urabones obtuse, moderately elevated, and scarcely recurved ; 

 anterior side produced, its border elliptically curved with the lower border ; superior 

 border nearly straight, of moderate length, sloping obliquely ; area flattened, transversely 

 lineated, divided by an oblique furrow, and bounded by two very small, minutely 

 tuberculated carina; ; escutcheon excavated, wide, its length is equal to half of that of the 

 marginal carina; the costated portion of the shell has very numerous closely arranged 

 concentric, raised, and minutely tuberculated costse. About thirty rows may be counted 

 in a specimen fifteen lines in length ; the first few costse appear to be destitute of tubercles ; 

 all the rows are nearly of equal size throughout their course, and are very closely arranged, 

 bordering upon the carina ; they do not quite reach the anterior border, but form a slight 

 undulation upon the anteal slope ; their posteal extremities rise nearly perpendicularly 

 towards the marginal carina. 



T. striata, Miller, and T. formosa, Lycett, are allied to it. Prom the first it is sepa- 

 rated by the smallness and obliquity of the area, and by the length of the superior border, 

 which offers a marked contrast to the short sub-quadrate figure of Miller's species. 



Prom T. formosa it is distinguished by the greater convexity, by the absence of the 

 acute recurved umbones, and by the concentric in lieu of the oblique costse of that species ; 

 the tubercles, also, are much more minute both upon the costse and the carina?, and, 

 contrary to T. formosa, the few first costse are plain. 



The height is about one sixth less than the length, but specimens differ in their 

 proportions ; no example with the valves united has been obtained. 



The figure given in the Monograph of the Great Oolite Mollusca (Palseont. Soc, 1853) 

 is unusually short posteally, which may have resulted from the position in which the 

 specimen was placed before the artist. 



Stratigrapldcal positions and localities. It has occurred in several distinct beds of the 

 Inferior Oolite near to Stroud very rarely, in cream-coloured, nearly hard limestone ; at 

 Desborough, Northamptonshire, in brown ferruginous oolite ; in white oolite at Stamford, 

 Lincolnshire, and in a similar rock at Stoke, near Grantham ; at Appleby, North Lincoln- 

 shire, in the lowest bed of Inferior Oolite, a hard, brownish oolite. Our specimens 

 fio-ured are from the latter locality, and were presented to me by the Rev. J. E. Cross; 

 the larger one is more lengthened than is usual ; at neither of these localities is it common. 



It is not certain that the species has been obtained at any foreign locality. Pine 

 specimens are in both of our great national museums, in the collection of the Rev. J. E. 

 Cross, of Appleby, and in that of the author at Scarborough. 



