﻿204 BRITISH FOSSIL TRIGONIiE. 



CJreensand possess similar features and reduce the supposed examples of T. Archaciana 

 to the little moulds exemplified, PI. XXV, fig. 1(5, from the Upper Greensand of the 

 Isle of Wight and of Warminster; these arc, however, altogether ill preserved and 

 doubtful as examples of that species. See also p. 141. 



I am also inclined to regard our specimens of T. Vicaryana as identical with the 

 7'. spinosa of D'Orbigny, which that author mistook for the T. spinosa of Parkinson and 

 of Sowerby ; no figiu'e has been given of T. Pi/rrha, D'Orb., but the few woi'ds of 

 description agree with the T. spinosa of British authorities. 



Trigonia signata, A(/. Page 29, Plate II, figs. 1, 2, 3. 



In the description of this species, p. 29, no allusion was made to the figure of T. 

 clavellafa in the work of Knorr (' Verst./ vol.ii, pi. B, fig. 1 a; 1775), which was referred 

 to by Agassiz as one of tlie types of his T. sipiata ; this omission resulted from a lack of 

 confidence in an engraving of one of the Cluvellulce in a work of such considerable 

 antiquity. 



The figures of T. clavellafa in Zieten's ' Die Versteinerungen Wiirtembergs' are 

 also quoted by Agassiz as one of his types of T. sipiata ; and, as they are free from 

 the objection above referred to, and also agree generally with British Inferior Oolite 

 specimens within slight limits of variation, and as the number of specimens collected 

 within the last thirty years from Yorkshire, Oxfordshire, and Gloucestershire are very 

 considerable and all approach nearly to Zieten's type, I preferred to regard the latter as 

 the species intended by Agassiz. 



In this arrangement we should regard the figure given by Agassiz, ' Trig.' pi. ix, 

 fig. 5, as a variety, excluding his pi. iii, fig. S, which represents a specimen very defective 

 in condition and doubtful as a species. The example given in ' Trigonies,' pi. ix, fig. 5, 

 is apparently founded upon Knorr's figure, and difiers as a variety from the figures by 

 Zieten ; it is remarkable for the much greater upward curvature given to the posteal 

 portions of the costal, which are also more attenuated; the same feature equally charac- 

 terises the imperfect specimen figured by Dewalque and Chapuis, ' Pal. Luxemb.,' p, 172, 

 pi. xxvi, fig. 1. As the two figures (Knorr's and Agassiz') above mentioned diflfer from 

 all the known British specimens, and the latter have a general unity of aspect and 

 accordance with Zieten's figures, I have adopted the last for the type of T. si(jnata. 



The description at p. 29 sufficiently records the diff'ering positions in the Inferior 

 Oolite in which the species has occurred ; it may, however, be mentioned that the 

 Upper Trigonia-grit of the Cotteswolds has supplied the specimens having the growth 

 most fully developed, and that in such the rows of costae anteally sometimes become 

 irregular and confused ; in specimens from otlicr positions in Oxfordshire and Yorkshire 

 the rows of costa; are remarkaljle for their regularity and uniformity. 



