CRICK : SPECIES OP NAUTILUS EKOM THE INFERIOR OOLITE. 1 35 



deep ; septa feebly concave, their inner (dorsal) portion projected 

 considerably forward over the preceding whorl ; suture-line with 

 a shallow lateral sinus, and a very shallow peripheral sinus. Siphuncle 

 extra-median, small. Test nearly smooth, with very fine growth- 

 lines, which have a nearly radial dii'ection on the lateral area, curve 

 backward near the periphery, and on the latter form a fairly deep, 

 obtusely V-shaped sinus. 

 Ditnensions. 



Diameter of shell .. . ... ... ... ... 99 mm. 



Height of outer whorl ... ... ... ... 58 ,, 



Height of outer whorl above preceding whorl .. . 37 ,, 

 Thickness ... ... ... ... ... about 69 ,, 



"Width of umbilicus ... ... ... ... 5*5 ,, 



Remarlcs. — This species is represented in the British Museum 

 Collection by only one example (No. C. 3183), the dimensions of 

 which are given above. This specimen lacks the body- chamber ; but 

 since the last loculus is shallower than those which precede, it is 

 probably an adult example. 



Ajjinities and Bijferences. — Compared with Nautilus rotundus,^ the 

 present species has less inflated whorls and a more prominent and 

 subangular umbilical margin ; this latter character is, however, much 

 less pronounced than in Nautilus Smithi? 



Form, and Loc. — The type-specimen (Wo. C. 3183) is labelled 

 ^^Sauzei-zone, Sherborne," but, judging from the matrix, Mr. Buckman 

 considers it to be "probably from the Iruellei -'bed. at Burton 

 Bradstock." 



10. Nautilus semiornatus, n.sp. Pigs. XIII & XIV. 



Tt/pes. — British Museum Coll., Nos. C. 3244 and C. 4499. 



Specific Characters. — Shell inflated, rather rapidly increasing; greatest 

 thickness almost close to the edge of the umbilicus, from about three- 

 fourths (in the less inflated form) to about four-fifths (in the more 

 inflated form) of the diameter of the shell ; height of outer whoid 

 a little more than one-half of the diameter of the shell. Whorls few ; 

 inclusion nearly complete ; umbilicus deep, about one-seventh of the 

 diameter of the shell in width in the more inflated form, a little 

 smaller in the less inflated form, with steep sides and subangular 

 margin. Whorl subquadrate in section, its height about two-thirds 

 of its width ; indented to about one-third of its height by the 

 preceding whorl ; periphery broad, feebly convex in the less inflated 

 form, in the more inflated form flattened and even slightly concave, 

 especially on the body-chamber, with obtusely angular margins ; sides 

 feebly convex ; inner margin rather wide, almost perpendicular to the 

 plane of symmetry, its inner half ' undercut,' well-defined from the 



^ Vide supra, p. 132. 



- A. H. Foord & G. C. Crick : Ann. & Mag. Nat. Hist., ser. vi, vol. v, p. 287, 

 fi-. 16. 



