370 
NAUTILOIDEA. 
Besides the specimeii figured (fig. 80, d) there are two other 
specimens of lower mandibles from the English Chalk (I^os. 32746 
and C. 70), but they are neither of them in a fit condition for illus- 
tration. Two upper mandibles from the Chalk of Ciply, Belgium, 
are also badly preserved \ one is a broad, and the other a narrow 
form. 
The Upper Grreensaud form here figured (fig. 80, e-g) must have 
belonged to a large IS'autilus. There are several of this type in the 
Collection, varying but little in size and precisely similar in form 
and markings. The largest (IS^o. 23270 a) is 1 inch 4 lines long, 
and 10 lines in its greatest breadth. 
Fig. 81. 
a, view of the inner side of an upper mandible, showing a conspicuous median 
longitudinal keel (the interruption near tlie apex is apparently due to 
fracture, because in another (smaller) specimen the keel is intact throughout 
its length) ; h, lateral view of the same specimen ; c, outer side, showing 
the central depression of the posterior part of the mandible. From the 
Cambridge Greensand, Cambridge. Drawn of the natural size from a 
specimen in the British Museum (No. 39626). 
Uemarlcs. This type of mandible is so strikingly like the one I 
have figured from the Neocomian of France (fig. 79, e-g) that 
there can be no doubt that they both belonged to a similar form of 
Cephalopod. Whether this was a Nautilus or not it is impossible 
to afiirm with certainty. There is here, at any rate, decided de- 
parture from the type of structure exhibited in other mandibles, 
the bulk of which latter may with much probability be ascribed 
to Nautilus — i. e., of course, in the restricted application of that 
term as employed in the present Catalogue. 
