﻿ADDENDA. 195 



narrow costse attenuated at both of their extremities, together with the considerable 

 angle which they form with the marginal carina. 



The specimen figured, PI. XXXIX, figs. 1 «, 2, exposes the diverging hinge 

 processes of the right valve which are unusually lengthened, more especially the posteal 

 one, which is upwards of eighteen lines in length, the entire border of the escutcheon 

 having a length of thirty-two lines ; the nymphal plate is also much lengthened. 



For the loan of this fine Trigonia I am indebted to W. H. Hudleston, Esq., who 

 states " that he obtained it in a limestone quarry at Cawklass, in the North Riding of 

 Yorkshire, in a compact calcareous stone full of sparry shells, and having a few oolite 

 granules. This rock belongs in all probability to the upper part of the Coralline Lime- 

 stones associated with Corals, though there are no Corals in this bed." 



The imperfect specimen, PI. XXXIV, fig. 5, is from the Coral Rag of Heddington, 

 near Oxford, and is deposited in the Oxford Museum. 



The smaller specimen, PI. XXXIV, fig. 6, has the outline nearly perfect ; it is from 

 the Elsworth Rock, Cambridgeshire, and belongs to the collection of Mr. J. F. Walker, 

 of York. 



Compared with the allied species T. AUna, the general figure has less convexity ; the 

 rows of costae are smaller and less curved, or become nearly perpendicular as they 

 approach the carina, and are much attenuated at each of their extremities ; the tubercles 

 in the rows are irregular and unequal. 



Trigonia Brodiei, Lye. PI. XXXV, figs. 8, 9 (Clavellat^). 



Trigonia striata, Quenstedt. Haiidbuch der Petrefactenkunde, tab. .xliii, fig. 13 



(not T. striata, Mill.), 1867. 



Shell smaller than T. striata, more oblong, with greater convexity. Umbones large, 

 prominent, obtuse, much recurved, placed one third the length of the shell from the 

 anterior border, which is convex and prominently rounded ; the superior or hinge-border 

 is lengthened and concave ; the area is narrow, transversely delicately striated, having a 

 mesial furrow, and bounded by minutely tuberculated carinas ; they form together with 

 the area a concave space at the hinge-border. The costge, about twelve in number, are 

 narrow and elevated ; their tubercles are small, closely arranged, irregular, rounded, and 

 attenuated anteally ; the rows of costae have considerable curvature, they are more widely 

 separated than is usual in allied species of the same group. 



As a British Trigonia this species appears to be rare ; my knowledge of it is limited 

 to the two specimens herewith figured ; the left-hand specimen is from the collection of 

 the Rev. P. B. Brodie, and was obtained by him in the Inferior Oolite (Northampton 

 Sands) of Milcomb Hill, Oxon., a locality described by Mr. Beesley, in his excellent 



