XAUTILID^. 
123 
18oo. Xaittihis {Discites) quadratus (pars), M‘Coy, British Palaeozoic 
Fossils, fasc. iii. p. 560. 
1863. Xautiliis suhmlcatus, F. Roeuier, Zeitschr. der Deiitsch. geol. 
Gesell. Band xv. p. 575, Taf. xiv. ff. 6«, 6 5. of Phillips.) 
1870. Xautihis subsulcatus, F. Roemer, Geologie von Oberschlesieu, 
p. 82. (Xot of Phillips.) 
1874. Xautilus quadratus, Young and Armstrong, Trans. Geol. Soc. 
Glasgow, vol. iv. pt. iii. p. 281. 
1876. Xauti/us [Discites) quadratus, Armstrong, Young, and Robertson, 
Cat. of Western Scottish Fossils, p. 59. 
Sjp. Char. “ Discoid, compressed, of little more than two volu- 
tions ; section of the whorls subquadrate ; the sides and periphery 
nearly equal in width, flattened, and at right angles ; the sloped 
sides of the umbilicus very steep, and about as wide as the inner 
margin between them ; periphery usually flat in the middle, and 
very slightly sloping at the sides towards the lateral angles, each 
lateral fourth bearing from one to five fine thread-like ridges (most 
usually the former number) ; sides sometimes nearly flat, or the 
half near the umbilicus moderately convex, and the outer half 
moderately concave ; but many specimens having each side obtusely 
ridged along the middle by two broad shallow sulci, while a few 
rare specimens have the sides divided into five coarse subequal 
ridges by three wider concave sulci ; occasionally also the middle 
part of the periphery is more prominent than the lateral thirds, and 
concave (sometimes all these varieties in a single specimen). Sur- 
face crossed by verj minute sigmoid strim on the sides, arched 
backwards on the inner half, also strongly arched backwards on the 
middle of the periphery (where, in perfect preservation, the trans- 
verse striae are crossed b}* minute spiral ones under the lens). 
Septa moderately numerous, their edges gently arched backwards 
on the sides and periphery ; body-chamber occupying half of the last 
whorl ; siphon small, close to the outer edge . . . {UrCoy.) 
liemarlcs. Two fragments of the body-chamber of this species in 
the Collection, from Scotland, exhibit the following characters : — 
The section is a little wider than high and subquadrate in form, 
the periphery is slightly rounded, its edges are bordered by sharp 
keels, and it has also two acute ridges or keels which mark off longi- 
tudinally a central space representing nearly one half of its area. 
Between these median keels and the edge of the periphery there is 
a very fine thread-like line. The sides of the shell are inflated below 
and somewhat concave above, a narrow ridge occupying the con- 
cavity. The edge of the umbilicus is separated by a shallow groove 
from the inflated part of the whorl. The sides of the umbilicus 
slope steeply down to the point of contact with the preceding wdiorl. 
