G. C. Crick—Two Chalk Cephalopods. B47 
identifies with Pachydiscus Sturt (Redtenbacher)' from the so- 
called Gosau Beds at Muthmannsdorf, Austria, a species which 
he also records from Mas de Blas Giner, near Alcoy (province of 
Alicante), Spain; in all cases in the Upper Senonian. 
The Lincolnshire specimen, although belonging to this group of 
forms, is easily distinguished by its wide umbilicus. Occurring at 
a lower horizon than the other species mentioned, namely, in the zone 
of Holaster planus, one would naturally expect to find a more widely 
umbilicated form. 
2. Herrroceras REUssIANuM (d’Orbigny).? (PI. X XVII, Fig. 3.) 
The specimen which seems to be referable to d’Orbigny’s genus 
Heteroceras was obtained by the Rev. C. R. Bower from the Holaster 
planus-zone at North Ormsby, Lincolnshire. In this genus there is 
a turreted portion as in Zurrilites, but the terminal portion of the 
shell is bent into the form of a hook. The present specimen 
(Fig. 3) appears to be a portion of the terminal hook of an example 
lying upon, and with one end partially imbedded in, a small block of 
chalk, the portion on the right-hand side being the anterior or apertural 
end. Close to this end of the hook there is a portion of a whorl of 
a turreted Cephalopod (marked a) that possibly originally belonged 
to the same specimen as the larger fragment. The hook, which has 
a total length of about 110mm. as measured along the median line 
of its periphery, does not lie quite in one plane, but has a double 
curvature; this character is exhibited more especially by the posterior 
portion of the hook that is only partially exposed and is shown on the 
left-hand side in the accompanying figure, this limb being apparently 
the one by which the hook was attached to the turreted portion of the 
shell, and therefore the younger portion of the hook. ‘he transverse 
section of the last portion of the shell (the part on the right-hand side 
in the accompanying figure) is a compressed oval, the ventro-dorsal 
and transverse diameters being 25 and 17 mm. respectively ; the cross- 
section of the other limb cannot be ascertained as it is partially 
imbedded in matrix, but the greatest width exposed is about 25 mm. 
The younger portion of the hook, excepting the inner or antisiphonal 
area, is ornamented with simple, rather oblique, and somewhat 
irregularly- -placed ribs, which pass uninterruptedly over the periphery, 
where they are about 2mm. apart; at irregular distances some of 
these are thicker than the rest and roughened and may originally have 
been produced into several small spines, but they are now too much 
abraded to state this with certainty; the later portion of the shell 
seems to have been ornamented with similar fine ribs, but at irregular 
intervals some of the ribs are greatly thickened on the outer portion 
of the lateral area and on the periphery of the whorl. The septa 
1 A. Redtenbacher, ‘‘ Die Cephalopoden der Gosauschichten ’’: Abh. d. k. k. geol. 
Reichsanst., Wien, Bd. v, 1873, p. 129, pl. xxx, fig. 10 (Scaphites Sturt). 
2 Hamites reussianus a Orbigny, Prod. de Paléont., vol. ti, 1850, p. 216.: This 
species was placed by Pictet and Campiche in the genus Anisocer as; by Schliter in 
the genus Heteroceras; and by Geinitz, Roemer, and Fritsch in the venus FHelicoceras. 
For 3 synonymy and references, see H. Woods, Quart. Journ. Geol. Soc. ., vol. lii,; 1896, 
pp. 74, 7d. 
