﻿SCABR^. 133 



upon the first-formed ten or twelve rows of costse. The lines of growth are delicate, 

 they are conspicuous upon the anterior face of the shell, and also upon the area and 

 escutcheon. . The test is thin and fraj^ile. The internal mould has its creneral fiirure and 

 outline so nearly resembling specimens with the test preserved that it is recognised 

 without difficulty ; its lower border has indentations produced by the extremities of 

 the costae ; the surface is usually plain, but sometimes it has faint impressions of the 

 costse ; the mesial furrow of the area is well defined. 



The specimen figured by D'Orbigny (pi. 290, figs. 1, 2) is of larger dimensions 

 than occurs in Britain ; the drawing is not altogether free from objection ; &<r. 2 has 

 the escutcheon too wide posteally ; it appears to form a deep concavity and gives no 

 sufficient indication of the considerable elevation of the superior border at the junction of 

 the valves ; the curved costellse upon the escutcheon and area are only about half as 

 numerous as in British specimens ; these features indicate a distinct variety if they are 

 faithfully depicted ; the small supplementary costellas upon the anterior face of the shell 

 are not noticed either in the figures or the description. 



Of the highly ornamented section of the Scahrm few forms can surpass in beauty and 

 delicacy the surface of the present species; the area and escutcheon more especially 

 present, under a magnifier, the semblance of a series of symmetrical, closely arranged 

 bead-like rows of necklaces, curving upwards at both of their attenuated extremities. It 

 will not readily be mistaken for any other Trigonia. 



Proportions. — The height is equal to four fifths of the length ; the diameter, through 

 the united valves, is equal to half the length. 



Stratigraphical position and Localities. — T. Filtoni is limited to the lower portion of 

 the Gault, which at Folkestone has produced a considerable number of the internal 

 moulds, to some of which the test is attached, but for the most part in portions 

 only. Well-preserved examples, therefore, rank as the most rare fossils of the Gault. 



France : in the sandy beds of Geraudet, Evry, Apothement, Macheromenil, 

 Seignelay. 



Trigonia pennata, Sow. Plate XXIV, figs. 4, o. 



Tbigonia pehnata, Sowerby. Min. Conch., vo]. iii, p. C3, tab. 237, fig. 6, 1819. 



— — Punch. Polens Palaeont., p. 60, 1837. 



— — Aijugsiz. Trigonies, pp. 9 and 52, 1840. 



— — Morris. Catalogue, p. 229, 1854. 



Trigonia pennata and Trigonia sulcataria are the only known British examples of a 

 small group of the ScahrcB, which is represented in France by other species and by 

 individuals the dimensions of which far surpass their British analogues; the British 

 Museum possesses a fine series of French specimens pertaining to this group. Like 



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