﻿150 



BRITISH FOSSIL TRIGONLE. 



In the North Riding of Yorkshire the Inferior Oolite occurs under other and peculiar 

 conditions, and hitherto has not revealed T. costata. At Blue Wyke the Dogger yields 

 numerous small valves, which have been attributed to this species, but their condition 

 of preservation is such as to preclude any rigid scrutiny ; upon the whole I am inclined 

 to refer them to T. denticulata, which occurs in some abundance in a bed of limestone 

 higher in the series upon the same coast. T. costata is absent in the Cornbrash of 

 Yorkshire, in which the Costata are represented by two other large species. 



A specimen of the typical form from the Cornbrash of Closworth has been kindly 

 forwarded to me by Colonel Mansel Pleydell; it differs in no respect from Inferior 

 Oolite examples. 



The specimens quoted by Agassiz are from the Cantons of Bale and of Soleure ; the 

 large specimens in Quenstedt's work (' Der Jura,' p. 502) is from Ehningen. 



In Southern Germany the species also occurs in the highest zone of the Lower Oolites 

 at Ehningen, associated with various Testacea well known in the Cornbrash of Britain. 



The localities, both British and foreign, assigned to T. costata are very numerous, 

 but as some of them do not appear to have been founded upon trustworthy specimens or 

 upon sufficient critical knowledge of the species, but little confidence can be reposed 

 in such determinations. The following remarks refer to specimens which have been 

 figured : 



The figures attributed to T. costata in the work of Knorr, Verst., Suppl., tab. 5 c, 

 figs. 3, 4, are coarsely engraved, and are scarcely trustworthy illustrations of any fossil 

 species ; they are certainly distinct from T. costata, but appear to agree with our 

 T. sculpta, to which they are referred. 



To the same species should be united the T. costata of the ' Encyclopedie Methodique,' 

 Supplement, table ccxxxviii, fig. 1 a, h. 



Also the figure of T. costata in the ' Lethaea Geognostica ' of Bronn, table xx, fig. 4. 



The T. costata of Zieten, ' Petref. Wurtemb.,' tab. cxxxvii, fig. 3 a, b, appears to agree 

 with T. denticulata. 



The T. costata of Parkinson, ' Org. Rem.,' vol. 3, tab. xii, fig. 4, is altogether 

 untrustworthy ; the costated portion of the valve may represent the typical form, but 

 the ornamentation of the area is a mere work of invention ; the same remark will 

 also apply to the surface-ornament of the escutcheon, the outline of which is also 

 erroneous. 



The T. costata of Smith, ' Strata Identified,' fig. 4, is a good representation of our 

 T. sculpta, var. Bolandi, from the Cornbrash of the southern counties, and also of 

 Lincolnshire. 



The T. costata of Young and Bird, ' Geol. Survey York. Coast,' tab. viii, fig. 19, is 

 T. Meriani, Ag., from the Coralline Oolite of Yorkshire and of the southern counties. 



The T. costata of Sowerby, in Grant's memoir " On the Geology of Cutch," ' Geol. 

 Trans.,' 2 ser., vol. 5, pi. 21, fig. 17, appears to agree with our T. elongata, var. lata. 



