﻿19S 



BRITISH FOSSIL TRIGONI/E. 



rows to appear widely separated — a feature which at once serves to separate it from 



T. imbricata. 



T. Witchelli has also some affinities with a little Kimmeridge Clay species kindly 

 communicated by Win. Topley, Esq., and known only from a partially exposed posteal 

 portion of the valve in black shale, brought up in the Sub-Wealden exploration from a 

 depth of 402 feet. The general figure appears to be similar, but the area has no median 

 carina ; the rows of costse are more closely arranged, their nodes are also larger ; each of 

 them is slightly prolonged or pointed downwards ; they are distinct in the rows : appa- 

 rently about a third part of the valves is exposed. 



Dimensions. The length of the largest specimen of T. Witchelli measured upon the 

 marginal carina is 9 lines ; the opposite measurement is 6 lines ; apparently the species 

 has but little convexity. 



Position and Locality. The few specimens obtained are ill preserved ; they are the 

 sole representatives of the genus hitherto known in the Fuller's Earth. The matrix is a 

 soft pale grey marly rock ; in the same bed were fragments of Ammonites Parkinsoni. 

 Hitherto this Trigonia has been obtained only at a single locality adjacent to the town of 

 Stroud. 1 



Trjgonia Snaintonensis, Lye, sp. nov. Plate XLI, figs. 1, 2. 



Shell having a resemblance in its general aspect and the surface ornaments to 

 T. recticosta (p. 16, PI. I, figs. 4 — 6), but having a much more considerable convexity ; 

 the area also differs materially in its more narrow figure and in the absence of a median 

 furrow; in the latter feature it exactly resembles T. gemmata (p. 15, PI. I, fig. 7), and 

 is similarly bounded by a plain marginal carina and a minutely papillated inner carina. 

 The first few rows of costae are concentric and tuberculated as in T. recticosta; the 

 others, whose perpendicular direction accords with those of the latter species, are larger, 

 more ridge-like, more elevated, and are much less distinctly and less regularly tubercu- 

 lated ; they are also somewhat fewer in number ; the whole aspect of the surface has, 

 therefore, much less neatness and minuteness in its ornamentation. 



The imperfect examples figured are almost the only specimens known ; they were 

 obtained by Mr. W. H. Hudleston, and are communicated for the present Monograph. 



1 "With much regret I announce that the two specimens so carefully figured on PI. XXXVIII were 

 lost on their return to Stroud through miscarriage of the post. It may be hoped that the loss is not 

 altogether irreparable, as, although the species has been obtained only at one locality, other specimens 

 are, I believe, in the cabinet of Mr. Witchell. I am not aware that in any other ins'ance a loss of fossils 

 has occurred in transmission through the post. 



