252 CATLALOGUE OF THE FOSSILS OF THE PERMIAN SYSTEM 
2. T. ScutotHemmir, Von Buch. 
Terebratulites lacunosus, Schloth., Schrif. der Mun. Ak., vi., 
pl. 8, £. 15-20. 
Terebratula Schlotheimii, V. Buch iiber Terebr., p. 39, pl. 
2, f. 32 ; Geol. Russ, ii., pl. vili., f 4 a, b, ¢, d, e. 
Shell subpentagonal; perforated valve flattened on the 
sides, deeply sinuated in the middle; imperforated valve tri- 
lobed, elevated in the middle in the part corresponding to the 
sinus in the lower valve, gradually depressed towards the 
margin; anterior margin produced horizontally in the 
sinus and on the sides to a considerable distance beyond 
the cavity of the shell; surface with 2, 3, 4, 5, or 6 more 
or less indistinct plaits, in the sinus, and as many on each 
side, covered with obsolete granulations, and a few distant 
stric of growth. 
In Magnesian-limestone ; common. Humbleton, Tunstall, 
Silksworth, Dalton-le-Dale. 
T. Schlotheimi occurs rather plentifully in the localities men- 
tioned above, and it is frequently associated with the two follow- 
ing species which appear to have been hitherto confounded with 
it. It is, however, easily distinguished from them by its neat- 
ness of form, by the narrowness of its sinus, the anterior part of 
which is higher than in either of the other species, and by the 
extensive development of the front margin in a horizontal direc- 
tion from the cavity of the shell. It is said to occur in the 
Zechstein of Germany, and in the Mountain-limestone of Russia. 
3. T. HuMBLETONENSIS, 7. s. 
Shell subtrigonal or obovate ; perforated valve with a 
broad sinus in the middle, rounded towards the lateral 
margins ; imperforated valve high in the middle, depressed 
towards the sides; the front margin of the sinus and 
sides produced horizontally a short distance from the 
cavity of the shell ; surface, with numerous plats in the 
sinus, which are sometimes bifurcated, and a few on the 
sides, granulated. 
In Magnesian-limestone ; not rare. Humbleton. 
Under this name we venture to separate some shells which 
