﻿ADDENDA. 



185 



Affinities and Differences. The nearest analogue of this grand species is T. navis, 

 Lam. ; the latter has the general figure shorter and more convex ; the anteal flattening of 

 the valve is more pronounced ; the escutcheon is wider, more excavated, and shorter ; the 

 smooth area and pallial rows of varices, attenuated upwards, are also very distinctive 

 features. 



T. scapha, Ag., a much smaller and shorter species, is characterised by the angularity 

 formed by the two portions of the varices about the middle of the valve, by the smaller 

 elevation of the umbo, by the absence of any distinct anteal flattening or truncation, and 

 by the greater breadth of the valve at the siphonal border. 



T. Robinaldina, D'Orb., from the Neocomian formation of Saint Sauveur (Yonne), one 

 of the Scaphoidea, has the general convexity much more considerable, so that the diameter- 

 through the united valves is equal to three fifths of the length ; the area is without 

 tubercles at the angle of the valve ; it has no median furrow and has no clear separation 

 from the pallial surface ; the escutcheon is short and has great breadth. 



Position and Locality. Our figure represents the largest known example of the 

 Scap/ioidea ; the original is a specimen in the British Museum which bears the inscription 

 Drift of Norfolk ; its history is unknown. The general aspect indicates that its original 

 seat was the Middle Neocomian formation of West Norfolk, a locality from whence 

 the specimens of T. ingens in the Lynn Museum were derived and probably also the 

 mould of T. scapha in the Woodwardian Museum last described. 



Trigonia pulchella, Ag. PI. XXXVIII, figs. 10, 11, 12, 12 a (Scaphoide^:). 



Teigonia pulchella, Agassiz. Trigonies, p. 14, tab. ii, figs. 1 — 7, 1840. 



— — llarcou. Recherches Gcologiques sur le Jura Salinois, Soc. 



Geol. de France, § 47, 1846. 



— — Terquem. Paleont. du Dep. de la Moselle (Extr. de la Stat. 



de la Moselle), p. 23, 1855. 



— — Quenstedt. Der Jura, p. 311, tab. xliii, fig. 1, 1857. 



— — Oppel. Jura-Formation, Wurtemb. Natur. Jahreshafte, 12 — 14 



Jahrg., p. 406, No. 426, 1857. 



— — Quenstedt. Handbuch der Petrefactenkunde, tab. xliii, fig. 14, 



1867. 



— — Lepsius. Beitriige zur Kentniss der Jura-Formation ina Unter 



elsass, p. 48, 1875. 



Shell small, subquadrate, moderately convex mesially, depressed anteally and posteally ; 

 umbones small, anterior, little elevated ; hinge-border lengthened, straight ; anterior side 

 perpendicular, abruptly truncated ; lower border slightly curved, having near to its posteal 

 extremity two or three short perpendicular folds corresponding with as many depressions 

 and prominences in the interior of the shell ; its extremity forms nearly a right angle with 



