﻿; ADDENDA. 



193 



Trigonia Alina, Cont. PI. XXXVIII, fig. 3 (Clavellatjs) ; also variety, PI. IX, 



fig. 2 (corrected). 



Trigonia Alina, Contejean. Etude de l'Etage Kimmeridien dans les environs de Mont- 

 beliard et dans le Jura de France et Angleterre, Extr. 

 Mem. de la Soc. d'Emulation du Do-ubs., pi. xiv, 

 figs. 3—5, 1859. 



— P. de Loriol, E. Royer, et H. Tombeck. Deser. G6ol. et 

 Paleout. des Etages Jurassiques superieurs de la Haut 

 Marne, Mem. Soc. Linn, de Normandie, torn, xiii, 

 fig. 5, pi. xvii, 1872. 



Shell ovately trigonal, convex, short anteally, lengthened posteally ; umbones anteal, 

 prominent, obtuse, much arched inwards. Hinge-border lengthened, slightly raised, its 

 posteal extremity forming an obtuse angle with the short siphonal border ; anterior and 

 lower borders curved elliptically. Escutcheon large, lengthened, and concave, its length 

 being equal to the height of the valve. Area narrow and flattened, its width not 

 exceeding that of the escutcheon ; it has the usual median furrow, and has transverse 

 irregular plications which enlarge slightly at their extremities, forming small bounding 

 elevations or carinas. 



The other portion of the shell has numerous, closely arranged rows of small nodose 

 varices (our specimen, a small one, has seventeen rows) ; their general direction have but 

 little curvature, but are not altogether regular and symmetrical in their course • their 

 posteal extremities form right angles with the angle of the valve which they touch ; the 

 nodes in the rows are small, rounded, closely arranged, often touching each other, and 

 vary little in size, excepting that the three or four rows last formed have the nodes larger 

 and less closely arranged ; but as our sole specimen is not of adult growth this feature 

 has but little significance ; the few first formed or umbonal rows are nearly plain or 

 slightly knotted. 



Compared with other allied examples of the Clavellata, the distinctive characters 

 consist of the narrow and nearly smooth area, the large escutcheon, the general figure of 

 the shell curved and lengthened posteally, the considerable number and close arrange- 

 ment of the small nodose costse, together with the small curvature which the rows make 

 upwards near to the angle of the valve. 



Upon comparing the original figure in the work of Contejean with that of de Loriol, 

 Royer, and Tombeck, some differences exist ; the latter has the rows of costas less 

 numerous, the tubercles are fewer or more widely separated in the rows, the diminution 

 in the size of the few last-formed costse is also a distinctive feature ; the general figure of 

 the shell has greater height, and is more attenuated at the posteal extremity ; it would 



