56 BRITISH SILURIAN BRACHIOPODA. 
Lincuvetta Davis, AL‘Coy (sp.). Pl. IV, figs. 1—16. 
Lingula, Davis, Quarterly Journal Geol. Soc., vol. ii, p. 71, 1846 ; Sedgwick, ib., vol. iii, 
pp. 140, 143, 147, 1847. 
Lineuua Davisi1, M‘Coy. Ann. and Mag. Nat. Hist., 2nd ser., vol. vin, p. 405; and 
British Paleeozoic Fossils, p. 252, pl. 11, fig. 7; also, when dis- 
torted, Tellinomya lingulecomes, ib., pl. i K, fig. 18, 1852. 
- ovata, M‘Coy (parte). Brit. Pal. Foss., p. 254, 1 1, fig. 6 (non L. ovata, 
M‘Coy), 1852. 
— Davisit, Salter. Siluria, p. 53, Woodeut foss. 9, fig. 11, 1859. 
Lixecutetta — Salter. Memoirs of the Geological Survey of Great Britain, vol. 
ili, p. 333, pl. ii, figs. 7—12, pl. iv, fig. 14, 1866. 
Spec. Char. Depressed, ovato-pentagonal, longer than wide; lateral sides almost 
parallel ; front nearly straight, or but slightly rounded; beaks obtusely angular, the slopes 
being almost straight; valves about equal, and very slightly convex; hinge-area in the 
ventral valve flat and rather broad, with a narrow groove in the middle. ‘The surface of 
the area, in the vicinity of the fissure, is horizontally striated and marked out by slanting 
lines. Internal surface marked with numerous pits, especially near the hinge-line. 
External surface covered with fine, sharp, concentric strize, or imbricating lamine. A 
large species ; one example measures 13 lines in length by 10 in width. 
Obs. Prof. M‘Coy and Mr. Salter have both bestowed much attention to the study of 
this species; they have also given us good descriptions, as far as the material in their 
possession would permit, of its external as well as of its interior characters. Although 
extremely abundant in the localities where it occurs, the shell is usually, or I might say 
almost always, more or less flattened and distorted, compressed or elongated, from the 
effects of pressure and cleavage, and, consequently, but rarely shows its true shape ; 
in some of these conditions it has even been mistaken by Prof. M‘Coy for a species 
of Zellinomya—T. lingulecomes [Salter]. Prof. M‘Coy states that its external sur- 
face is marked “with numerous faint, concentric, rather wide, sub-angular undulations 
of growth, accompanied by irregular, concentric, imbricating lamin; striae ten in one 
line on the exterior of the shell; no trace of longitudinal external striz, but on the in- 
ternal cast a few faint, obsolete, flattened, fibrous radiations, observable with the lens; 
. . . this curiously wide satchel-shaped Zingu/a is the species discovered by Mr. Davis 
in such profusion in the Lingula-slates near ‘Tremadoc. .. . . The British species 
most allied to this is the Z. attenuata, Sow., which, however, is easily distinguished by its 
much longer, trigonal, retrally narrowed form, rising from the gradual passage of the sides 
into the posterior lateral margins (without angulation), the very prominent, narrow, gibbous 
form of the beaks, &e. The substance of the shell is very thin, and the traces I have seen, 
apparently of the mesial ridge, extend little more than one third the length of the shell. 
