122 



PEOCEEDIjSTGS of the MA.LACOLOGICAL SOCIETY. 



It is not so robust as tlie specimen of JV. clausus, from tlie D'Orbigny 

 Collection in the Museum of Natural History, Paris, wliicli is figured 

 in Ann. & Mag. Nat. Hist., ser, ti, vol. v, p. 284, fig. 14, and Cat. 

 Toss. Ceph. British Museum, pt. ii, p. 225, and its umbilicus is not 

 closed by a shelly callus as in that example, but it has a broader and 

 more flattened periphery than D'Orbigny's figure of the species in his 

 Pal. rran9. Terr. Jur., vol. i, pi. xxxiii. 



Form, and Loc. — Inferior Oolite [Parkmsom-zonc) : Vetney Cross, 

 Dorset. 



Deslongchamps' specimen came from the "zone a Ammonites 

 Murchuotice (couches de recif) de May." 



3. Nautilus ruscus, n.sp. Pigs. lY & Y. 



Types.— British. Museum Coll., Nos. C. 4493 and C. 4494. 



Specific Characters. — Shell rather small and robust, not very rapidly 

 increasing, somewhat hexagonal in transverse section : greatest thick- 

 ness — in the more inflated form, at about two-sevenths of the width 

 of the lateral area from the edge of the umbilicus, about seven-tenths 



Fig. IV. — Nautilas fiiscus, n.sp. a, lateral view of an example of the more inflated 

 forms ; b, peripheral view of tlie same, showing the distinct growth-lines on 

 the periphery. Inferior Oolite : Burton Bradstoek, Dorset. Drawn from an 

 example in the British Museum Collection [C. 4493]. Natural size. 



of the diameter of the shell ; in the less inflated form, somewhat nearer 

 the edge of the umbilicus, and about three-filths of the diameter of 

 the shell. Whorls few, exact nuaiber not known ; inclusion nearly 

 complete ; umbilicus from about one eighth (in the more inflated form) 

 to about one- seventh (in the less inflated form) of the diameter in 

 width, with subangular margin, deep, exposing the edges of the inner 

 Avhorls. Whorl trapezoidal in section, wider than high ; indented to 

 about one-third of its height by the preceding whorl ; periphery broad, 

 slightly convex in centre, feebly concave near each margin, about one- 

 half of the diameter of the shell in width, with prominent subangular 

 margins ; sides feebly concave near the periphery, the rest rather 

 convex; inner area (or umbilical zone) steep, almost perpendicular 

 to the plane of symmetry of the shell. Body-chamber occupying 



