266 
DEVONIAN FAUNA. 
The species was named by Goldfuss without a description in von Dechen's 
' Handbuch ' in 1832 ; but in 1842 it was independently described by two otlier 
authors under two difierent names. It is a matter of some difficulty to determine 
which of these two latter has the priority ; but from the facts stated below 
(p. 284) it appears most probable that it lies with d'Archiac and de Verneuil. 
Sandberger, in his later work, though asserting that his name has the priority, 
withdraws it in favour of d'Archiac' s as being the more suitable. 
Affinities. — ScoUostoma texata, Milnster, sp., has a much higher spire and a 
much sharper, though somewhat similar, ornamentation. The shape of its mouth, 
moreover, shows it to be quite a different kind of shell, so that the similarity of its 
markings is only superficial. 
The shape of the mouth resembles that of Plagiothyra archon, which differs 
in its surface being almost smooth. 
Delphinula funata, Goldhiss,^ from the Coralline Oolites, is very similar in orna- 
ment, but it is a shorter, more globular shell, with a totally different mouth and 
with an umbilicus. 
Naticopsis Gicma, Vern., sp.,^ is according to Barrois^ a more elongate form, 
with a larger body- whorl. 
2. Plagiothyra aechon, Whidborne, sp. PI. XXVI, figs. 6, 6 a, 7, 7 a, 7 h. 
1889. MoNODONTA AECHON, Wlddlome. Geol. Mag., dec. 3, pt. 6, p. 30. 
Description. — Shell large, elevated, trochiform, consisting of few and quickly 
expanding whorls. Suture almost linear. Whorls nearly flat, spreading at once 
obliquely down from the suture, with a row of low indistinct nodules immediately 
below it, and then becoming first slightly concave, and then slightly convex until 
they suddenly curve to form the flat base of the shell, which is apparently with- 
out an umbilicus. Mouth entire, bluntly triangular, very oblique, so that the 
plane through it slopes backwards and downwards at an angle of more than 45°. 
Outer lip sharp. Inner lip diffuse and concave, spreading over a large part of the 
base of the shell, and bearing a single broad, low, flat tooth in its centre. 
Surface ornamented with a few, coarse, regular growth-lines, sloping obliquely 
backwards from the sutures. Shell- structure thick. Colour black (?). 
Size. — Height 85 mm., width 45 mm., in a specimen in which the apical 
whorls are absent. 
Locality. — Chudleigh. Three specimens in Mr. Vicary's Collection. 
1 1844, Goldfuss, ' Petref. Germ.,' vol. iii, p. 89, pi. cxci, fig. 11. 
2 1846, Verueuil, ' Bull. Soc. Geol. Fr.,' ser. 2, vol. iii, p. 455. 
3 1882, Barrois, ' Mem. Soc. Geol. Nord,' vol. ii, No. 1, p. 346, pi. xvii, figs. 15^7, h. 
