imperfectly-defined Species of Jurassic Nautili. 267 



Museum, Cambridge, and those also of the Museum of Prac- 

 tical Geology, who lent us specimens from their valuable 

 collections. It may be added that all the illustrations accom- 

 panying this paper were drawn by one of us upon the wood 

 (upon a reduced scale) with the aid of a camera, by which 

 means accuracy of outline is secured. 



We are again indebted to the kindness of Dr. Woodward, 

 F.R.S., for the use of the woodcuts illustrating this paper. 



Appended is a list (p. 266) of the species of Jurassic Nautili 

 contained in the British Museum. The new and revised species 

 are placed in the first column, and in the second those which 

 do not require revision and are therefore not described in the 

 present paper ; of each of the latter, however, we give the 

 reference to the original description. 



Lias. 



1. Nautilus simillimuS) sp. nov. 



Fis:. 1. 



Biiilil 



ill 





Nautilus simillimus. — a, lateral view of a young individual, showing- the 

 closed umbilicus ; 1>, peripheral view. Drawn from a specimen in the 

 British Museum. Nearly two thirds natural size. 



Sp. char. Shell somewhat compressed on the sides, nar- 

 rowly rounded on the periphery, completely involute. Um- 

 bilicus closed by a shelly callus. Septa moderately distant ; 

 sutures slightly curved on the sides of the shell and forming 

 a shallow sinus upon the periphery. Siphuncle unknown. 

 Test ornamented with fine, close-set, subregular, wavy, lon- 

 gitudinal ridges, which are somewhat coarser on the sides of 



20* 



