CEICK : SPECIES OF NAUTILUS FEOM THE INFEEIOR OOLITE. 



129 



horizon than that which has yielded the example (Ko. C. 4495) here 

 referred to JV. subsimcatus, D'Orb. 



Affijiities and Differences. — This species comes very near iV. suh- 

 sinuatus, D'Orb. (iV. simiatus, J. Sowerby), but it is more robust 

 and has a slightly different suture-line. In what is here regarded 

 as Sowerby's species the inner side of the lateral sinus of the suture- 

 line is straighter, and the outer side more curved, than in the present 

 one, so that in this the lowest part of the sinus is further 

 from the umbilicus than in Sowerby's species; the saddle near the 

 umbilical margin is also wider in the last named. If subsequent 

 observations should prove that the two forms occur in the same beds, 

 the differences are so slight that they may then perhaps more correctly 

 be regarded as merely sexual. 



Form, and Log. — Inferior Oolite (^^ con cav us -zone : probably Hyper- 

 Uoceras-hQ^.''^ — S. S. Buckman) : Bradford Abbas, Dorset. 



Fig. IX. — Nautilus impendens, n.sp. a, lateral view of the type -specimen ; 

 b, peripheral view of the same. Inferior Oolite : Bradford Abbas, Dorset. 

 Drawn from the specimen in the British Museum Collection [C. 4502]. 

 About one -half natural size. 



6. Nautilus impendens, n.sp. Fig. IX. 



Ty;;e.— British Museum Coll., No. C. 4502. 



Specific Characters. — Shell compressed, somewhat rapidly increasing ; 

 greatest thickness near the umbilical margin, rather more than one-half 

 of the diameter of the shell ; outer whorl about seven-twelfths of 

 the diameter of the shell. Whorls few ; inckision nearly complete ; 

 umbilicus narrow, about one-twelfth of the diameter of the shell in 



