300 
DEVONIAN FAUNA. 
synonymy) evidently does not belong to this species, as it has sharp angulated 
whorls and a much smaller umbilicus. 
PI. elliptica, Miinster,^ has a narrow concave sinus-band upon an elevated rim. 
PI. undulata, F. A. Romer/ seems to have much flatter sides, more angulated 
whorls and a much narrower sinus-band. Ferd. Romer^ considers it distinguished 
by its shortness and its triangular mouth. Some specimens of the present shell, 
however, are certainly very short. 
PI. plena, Hall,* is a more exactly conical shell, less umbonated, with a lower 
sinus-band, which is partially covered by the succeeding whorl, and with fine 
transverse striae only. 
PI. EoUubanica, Tschernyschew,^ is a small shell which differs in having spiral 
ridges on the upper part of the whorls and a still wider sinus-band. 
15. Plbueotomaeia dissimulatrix, n. sp. PI. XXVIII, fig. 17. 
Bescriftion. — Shell large, turbinate, rather elevated, of three or four volutions. 
Spire increasing rather quickly. Suture deep, rectangular. Whorls sub-circular 
in section, nearly flat at the suture, and most convex on the shoulder and at the 
lower angle. Body-whorl very much swollen. Sinus-band narrow, elevated, 
bounded by indistinct ridges, situated in the centre of the back. Ornament 
consisting of coarse, oblique, rounded, transverse ridges, arching back from the 
suture, and apparently of one or two coarse indistinct spiral ridges near the sinus- 
band. 
Size. — Height, 38 mm. ; width about 38 mm. 
Locality. — Wolborough. There are four very defective specimens in the 
Museum of Practical G-eology, and a very doubtful specimen in the British Museum. 
Bemarhs. — Only two of these specimens show much character; the others 
being almost unrecognisable. Even these are too obscure to permit a complete 
definition of the species, or even certainty as to its true position. The distinctive 
features are the narrow elevated sinus-band, the sub-quadrate or sub-circular 
section of its whorls ; and the coarse oblique strise. As in these points it differs 
from PI. delphinuloides, I do not think it can be regarded as a variety of that 
shell. It more nearly approaches PL victrix, but the shape and the ornamentation 
are apparently different, the spiral lines dominating in the one, and the oblique 
1 1844, Groldfuss, 'Petref. Q-errn.,' vol. iii, p. 67, pi. clxxxiii, fig. 9. 
2 1843, F. A. Eomer, ' Verst. Harzgeb.,' p. 28, pi. vii. figs. 10 a, b. 
3 1844, F. Eomer, ' Ehein. Uebergangsgeb.,' p. 80. 
* 1879, Hall, 'Pal. N. Y.,' vol. v, pt. 2, p. 66, pi. xvii, figs. 11—13. 
5 1887, Tschernyschew, ' Mem. Com. Geol. Euss.,' vol. iii, No. 3, p. 170, pi. 6, figs. 10—11. 
