﻿ADDENDA. 



209 



Trigonia iMBRicATA, Sow. Plate VI, fig. 5; Plate XXXVI, figs. 9, 10; also Plate 



XLI, figs. 10, 11, U, p. 33. 



The figures on Plates VI and XXXVI represent specimens obtained in the Great 

 Oolite of Anclifi', and do not sufficiently express the little perpendicular pillars or 

 elongations of the tubercles downwards in each, features which characterise the species. 

 The figures on Plate XLI are drawings of Fullers Earth specimens, deprived of the 

 test ; they nevertheless expose the little characters indicated, and it is hoped therefore 

 that they will aid in illustrating this species. The specimens have been procured by Mr. 

 Witchell, who has kindly forwarded them to me to be used in this Monograph. Compared 

 with an allied species, T. tuberculosa, Plate V, figs. 9, 10, the latter has the rows of 

 tubercles much more closely arranged, and the area has transverse striations in lieu of 

 the widely separated costellse of T. imbricafa. 



Localify. — The Fullers Earth of Stroud, associated with Trigonia Witchelli, Posi- 

 donomya opalina, Sowerbya triangularis, and other Conchifera. 



Trigonia Bronnii, Ag. 



At p. 23 is a description of this species founded upon examples from the Coral Rag 

 of Glos, Normandy. Professor Hebert, in his ' Memoir on certain Clavellated Trigonise of 

 the Oxford Clay and Coral Rag,' there quoted, refers to four British specimens of 

 T. Bronnii obtained in the Calcareous Grit of Weymouth. On examination some small 

 examples of clavellated forms from the latter locality, in which the rows of costse are 

 nearly horizontal, appeared to coincide with some French examples of T. Bronnii, a 

 species which has considerable variability even when obtained from a single locality. 

 Subsequent comparisons and examinations of various Weymouth and French specimens 

 have convinced me of the fallible character of this single distinctive feature, and of the 

 necessity of merging all such Weymouth specimens in T. clavellata, to which species, 

 therefore, fig. 8, Plate IV, should be referred ; and T. Broiinii should be removed from 

 the list of British species. 



The subjoined figures represent a common or medium-sized example of T. Bronnii 

 from Glos. 





Trigonia Bronnii, Ag. 



