CEPHALOPODA. 9 



The specimen figured appears to be the same as the B. Bessinus, D'Orb., from the Inferior 

 Oolite of Port-en-Bessin (Calvados) ; the general proportions are similar, about eight times 

 as long as wide, and the division of the furrow may be faintly traced in some specimens. 

 It is probably identical with the shell figured by Professor Buckman (loc. cit.) as B. cana- 

 licatus, Schlot, but that species is stated by M. D'Orbigny to have an equally impressed 

 furrow, whereas, in our specimens, it is always expanded towards the point of the rostrum. 



Locality. The Stonesfield slate of Stonesfield, and Sevenhampton near Cheltenham. 



Order — Tetrabranchiata. Owen. 



Family — Nauti li d^e . 



Nautilus, Linnceus. 



Bisiphites, Oceanus, Be Montfort. 

 Omphalia, Be Haan. 

 Nautilites, Schlotheim. 



A discoidal, convoluted, multilocular shell, compressed or ventricose, with contiguous 

 volutions, the last one generally concealing the others, septa transverse, concave, and some- 

 times sinuous, with entire margins, more or less centrally perforated in their disc. 



Nautilus dispansus. Plate II, figs. 5, 5«. 



N. Testa subglobosd, late umbilicatd, anfractibus rotundatis, lateraliter subcarinath ; 

 aperturd dilatatd, subovali ; septis (?),sip/iunculo (?). 



A somewhat globose and smooth shell, with rapidly increasing volutions, and a large 

 and rather deep umbilicus, exposing the previous volutions ; umbilicus occupying about 

 one third of the diameter of the shell ; volutions rounded on the back, and slightly cari- 

 nated towards the base by the obliquely flattened form of the outer margin of the 

 umbilicus. Aperture expanded, arched, semi-ovate, wider than high. 

 Septa and Siphuncle not visible in the specimen described. 



Diameter of the aperture . . . Clinches 



Height of the „ . . . 3| „ 



Volutions increase in size (increasing about § in the 



volution), from . . . . 2£ to G| in. 



Height of re-entering volution . . 1 „ 



This species is closely related to N. excavatus, Sow., ' Min. Con.' tab. 529, f. 1, from the 

 Inferior Oolite of Dorsetshire ; but it is readily distinguished from it by the more oval form 

 of the aperture ; the width of the umbilical opening, in proportion to the diameter, is also 



