﻿SCABRiE. 



135 



posteal costse are smaller • they occupy a larger ante-carinal space and are more faintly 

 defined. 



Dimensions. A specimen of the largest size has the length 10| lines ; height 

 9 lines ; usually the dimensions are much less, or nearly coincide with the type-specimen 

 of Sowerby. 



Stratiyraphical positions and Localities. This small and well-characterised species 

 appears to be rare. Mr. C. J. A. Meyer has obtained it at Dunscomb Cliffs, to the 

 eastward of Sidmouth, in Sandy Chloritic Marl ; Mr. Cunnington has a fine specimen 

 reputed to have been obtained in the vicinity of Folkestone ; Mr. Vicary has collected 

 several specimens in the pebbly bed (Upper Greensand) which overlies the Greensand at 

 Great Haldon. The type-specimen of Mr. Sowerby, now in the British Museum, is from 

 Teignmouth. T. pennata is usually accompanied by the following congeneric forms — 

 T. sulcataria, T. Vicaryana, and T. Meyeri. It therefore pertains to a higher position 

 than the Greensand at Blackdown and Haldon, or to the Upper Greensand and 

 Chloritic Marls of South Devon. 



Trigonia sulcataria, Lam. Plate XXVI, fig. 8. 



Trigonia sulcataria, Lamarck. Anim. sans Vert, torn, vi, p. 92, No. 9, 1819. 



— — Defrance. Diet, des Sc. Nat., torn, lv, p. 295, 1828. 



— — Deshayes. Edit. Lamarck, torn, vi, p. 517, No. 9, 1835. 

 Lyrodon sulcatum, Gold/. Petref. Germ., vol. ii, tab. 117, fig. 7, 1836. 

 Trigonia sulcataria, Agassiz. Trigonies, p. 33, pi. xi, fig. 17, 1840. 



— — D'Orbigny. Paleont. Fran., Terr. Cret., vol. iii, p. 150, pi. 294, 



figs. 5-9, 1843. 



— — D'Orbigny. Prodrome de Pale'ont., vol. ii, p. 161, No. 325, 1850. 



This, our second and larger species of the pennata group, differs from T. pennata in 

 the general figure, which is much shorter posteally, larger and more inflated anteally ; 

 the umbones are more nearly mesial, more elevated, and more recurved ; the costae 

 are somewhat fewer (about 24), larger, more distantly arranged, shorter, and directed 

 somewhat obliquely downwards posteally ; the ante-carinal space, which is occupied 

 by the posteal perpendicular costellse, is more depressed ; it extends upwards even to the 

 apex of the valve. The area is shorter, so that the angle of the valve has a greater 

 curvature ; its costellse are very delicate and closely arranged ; they are limited to the 

 upper half of the area, the lower portion of which is plain ; it is traversed by a distinct 

 mesial furrow. The escutcheon is large, slightly concave, and only indistinctly separated 

 from the area, the delicate costellse of which traverse the escutcheon also, transversely and 

 with increased prominence. 



