﻿136 



BRITISH FOSSIL TRIGONLE. 



Agassiz placed T. sulcafaria in the section of the Undulates probably from the angles 

 formed by the two series of costse ; but on the other hand he placed T. pennata with 

 the Costatce. The present arrangement of the group with the Scabra is founded upon the 

 crenulations of the costa3 and the presence of crenulated transverse costellge, which cross 

 both the escutcheon and area, together with the absence of bounding carina? to the area; 

 whereas in the Undulata the escutcheon is invariably plain. Agassiz has also made 

 T. sinuata, Park., a synonym of T. sulcataria, 'Trigonies/ pp. 33, 34. I do not 

 perceive even a remote resemblance in Parkinson's shell, which is well figured in his 

 ' Organic Remains,' to the T. sulcataria of Lamark. 



Stratigraphical position and Localities. In Britain T. sulcataria is rare and usually 

 badly preserved. Mr. Meyer has procured specimens in Chloritic Marls at Dunscomb 

 Cliffs associated with T. pennata and T. Meyeri ; Mr. Vicary has also obtained it 

 associated with T. pennata in a pebbly bed with Greensand fossils overlying the 

 Greensand at Great Haldon. Hitherto no British specimen having the test preserved 

 and its outlines perfect has come under my observation ; their condition is that of 

 well-preserved moulds of external casts which have no traces of the perpendicular 

 plications upon the costse nor of the lines of growth upon the ante-carinal space ; the 

 costellae upon the area cover a larger portion of its surface than is shown in the figures 

 of Goldfuss, of D'Orbigny, and of Agassiz ; the figure given by the latter author presents 

 differences both in the posteal or perpendicular costse and in the area, which indicate a 

 distinct species. It is intended to figure a second specimen of T. sulcataria from Great 

 Haldon upon a future plate. 



French specimens of much larger dimensions and in a fine state of preservation occur 

 in the Greensand of Le Mans. The British Museum has a good series of examples from 

 that locality, numbered " 34,888." There are also two fine examples of an allied species 

 named T. Nereis, D'Orb., ' Prodr. de Paleont.,' vol. ii, p. 162, No. 322. Of equal 

 size to T. sidcataria, it differs in having the surface ornaments far more minute and 

 delicate ; it differs also from the brief description given by D'Orbigny in having 

 the ante-carinal space similar in character to that in T. sulcataria ; in T. Nereis the 

 space is stated to be plain. 



Trigonia spinosa, Park. Plate XXIII, fig. 10; Plate XXIV, figs. 8, 9; moulds of 



external casts, Plate XXVIII, figs. 1, 2. 



Trigonia spinosa, Parkinson. Org. Rem., vol. iii.pl. xii, fig. 7, 1811. 



— — Sowerby. Min. Conch., vol. i, tab. lxxxvi, p. 196, 1815. 



— — Pusch. Polens Palseont., p. 60, 1837. 



— Pyrrha, D'Orbigny. Prodrome de Paleont., vol. ii, p. 161, No. 326, 1850. 



— spinosa, Morris. Catalogue, p. 229, 1854. 



— — Phillips. Geology of Oxford, p. 439, 1871. 



