282 
DEVONIAN FAUNA. 
4. Pletjkotomaeia impbndens, Sowerby. PI. XXVII, figs. 13, 13 a. 
1840. Pleurotomaeia iMPEifDENs, Sowerhy. Geol. Trans., ser. 2, vol. v, pt. 3, 
pi. Ivii, fig. 16. 
? 1841. — — Phillips. Pal. Foss., p. 98, pi. xxxvii, figs. 
180,180*. 
1854. — — Morris. Catal. Brit. Foss., p. 273. 
? 1861. — Hebe, Hall., Eep. N. T. State Cab. Nat. Hist., p. 105. 
? 1862. — _ _ Fifteenth Eep. N. Y. State Cab. Nat. Hist., 
pi. V, figs. 7 and 8. 
? 1876. — — — lUust. Dev. Fos., pi. xix, figs. 2—7. 
? 1879. — — — Pal. N. T., vol. v, pt. 2, p. 68, pi. xix, 
figs. 2—7. 
Description. — Shell of moderate size, turbiniform. Spire forming a low convex 
cone of about four slowly increasing volutions. Apex obtuse. Suture rather 
shallow and obtuse. Whorls semi-elliptic, sloping out obliquely and very convexly 
to their widest part, where they become perpendicular for a short distance 
above the lower suture. Body- whorl large, curving rapidly round the back, and 
becoming obliquely convex on the base. Sinus-band super-sutural, broad, 
consisting of three prominent close rounded ridges, divided by two narrow 
grooves. Ornament consisting of about ten close, low, rounded ridges above the 
sinus-band, crossed by numerous, close, flatly-rounded threads, which arch 
obliquely backwards on the upper part of the whorls, and become almost invisible, 
on the sinus-band, where they appear to be recurved. Umbilicus small or absent. 
Mouth unseen. 
Size. — Height 18 mm., width 22 mm. 
Localities. — There is a specimen in Mr. Champernowne's Collection from 
Lummaton, and a cast in Mr. Vicary's Collection from Wolborough. 
Remarks. — This appears to be the shell imperfectly described by Sowerby 
from Plymouth, though his figure and description are not clear enough to permit 
any very great certainty. Our specimens are obscured round the base, which 
seems on the whole convex, though there may have been a concavity round the 
umbilicus. Sowerby speaks of the base as concave ; but in other respects his 
description appears to agree with the present fossils. 
The ornament of the shell appears to be very distinct. The spiral marks 
dominate, and the narrow furrows between the close ridges quite cut the longi- 
tudinal threads. As the lower part of the body-whorl and the base of Mr. 
Champernowne's specimen are decayed, the ornament on that part of the shell is 
unknown. 
