﻿ADDENDA. 



197 



Jour. Geol. Soc.,' vol. xxiii, p. 227, 1867 ; vol. xxiv, p. 218; also vol. xxvi, p. 326, 

 1870. 



The difficulties attendant upon the examination of Clavellated Trigonia with fragile 

 crystalline tests preserved in a hard matrix have necessitated the use of specimens 

 defective in their outline, but otherwise in a fine condition of preservation ; they were 

 obtained in the vicinity of Tealby, in the bed of hard limestone which has also yielded 

 T. Tealbyensis, a bed distinct from the brown ferruginous pisolite of the same locality, 

 which is the source of the specimens of T. ingens, PI. XXXVI, figs. 5, 6. The originals 

 of T. Keepingi are in the Woodwardian Museum, Cambridge, and had not been dis- 

 covered when p. 24 was printed, where T. ingens is stated to be the only example of the 

 Clavellata known in the Cretaceous Bocks. The general aspect of these clavellated 

 forms is such that they would readily be mistaken for Jurassic Trigonia in the absence 

 of all knowledge of their geological position — a fact which appears to lend some support 

 to the views of those palaeontologists who would arrange the Neocomian formation with 

 the Upper Jurassic rather than with the Cretaceous Rocks. One distinctive feature 

 exemplified in these delicately preserved Trigonice consists in the lines of growth having 

 their edges minutely and densely fringed or granulated, visible only under a magnifier, 

 and resembling a similar feature in the Cretaceous Glabra, as in T. excentrica; a kind of 

 surface which is absent in the Jurassic Clavellatce, and is distinct from the epidermal 

 tegument which is not preserved. 



Trigonia Witchelli, Lye, sp. nov. PI, XXXVIII, figs. 8, 9. (Clavellat.e.) 



For examples of this small species I am indebted to Mr. Witchell, of Stroud, who 

 discovered them in the Fuller's Earth of that locality ; their condition of preservation is 

 only indifferent, the test is not preserved, the ornaments of the surface are in relief upon 

 a black pigment, which renders them distinct and prominent, notwithstanding their 

 minuteness and delicacy. They possess some general resemblance to T. imbricata, PI. 

 XXXVI, figs. 9, 10, but are sufficiently distinct. Compared with that little species, they 

 are larger, more lengthened, and pointed posteally ; the umbones are more elevated 

 and produced ; the surface ornaments are more minute. 



The area is narrow, having three very small plain, linear carinas, and is traversed 

 transversely by a few widely separated, regular costellae. The escutcheon is narrow, its 

 superior border is somewhat raised. Upon the sides of the valves the row r s of tuber- 

 culated costae, about 9 or 10 in number, are concentric, much curved, equal in size, 

 small, and minutely papillated. The larger specimen has two of the costae with their 

 anteal portions broken, and their papillae scattered irregularly ; their figures are slightly 

 lengthened and pointed downwards. The very diminutive size of the costae causes the 



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