68 C. P. Chain-in 8f T. H. Withers— Fauna of the Chalk Rock. 



PuzosiA cuRVATisuLCATA, sp. hov. (Plate II, Figs. 1-4.) 



Description. — AVhorl very slowly increasing, laterally-compressed 

 oval in transverse section, width three-quarters the height, indented 

 to about a quarter of its height by preceding whorl, inner half of sides 

 somewhat flattened, the outer half sloping gradually towards the 

 periphery, periphery broadly convex, umbilical margin not veiy clearly 

 defined, umbilical zone feebly convex, steeply inclined towards the 

 umbilicus. There are no indications of the test, but on the anterior 

 portion of the larger specimen (Fig. 1) are seen distinct indications 

 of broad, feebly-convex ribs which are disposed in a forwardly-directed 

 curve and which seem to disappear at about the middle of the sides. 

 On both pieces a pronounced constriction is seen, being deeply, but not 

 sharply, incised at the umbilical margin, whence it extends radially to 

 about the middle of the side, where it becomes more shallow and 

 assumes a forwardly-directed curve towards and over the periphery. 

 The suture-line is well seen in the smaller specimen (Fig. 3), and is 

 reproduced in Fig. 4. In the larger specimen only part of the 

 external saddle, the first lateral saddle, and the intervening first 

 lateral lobe are seen. 



Dimensions. — Larger fi'agment is 64 mm. in length measured along 

 the centre of the periphery. Height of whorl 55 mm. Height above 

 preceding whorl 42 mm. ; thickness 43 mm. Smaller fragment 46 mm. 

 in length measured along the centre of the periphery. Height of whorl 

 36 mm. Height above preceding whorl 28 mm. ; thickness 29 mm. 



Affinities. — The species differs from Puzosia plamdata in the 

 curvature of the constrictions not being sigmoidal, and in the less 

 prominent and more distantly disposed ribs. The flattening of the 

 sides of the whorls in P. plamdata extends nearer the periphery than 

 in this species, and the slope of the umbilical zone is more steep. 



In the Cretaceous of India several species of Puzosia occur, and 

 Stoliczka ^ has recognized two varieties of P. plamdata — (1) a strongly 

 compressed form with fine ribs, (2) a thicker sub-species with stronger 

 and less numerous ribs. Our specimens come nearer the former, which 

 was separated by F. Kossmat ^ and referred to P. gaudama, Forbes, 

 which is the only species found as high up as the Turonian. Compared 

 with P. gaudama, the whorls in our specimens are much stouter and 

 much more rounded on the periphery. The ribs are farther apart and 

 less forwardly directed, while the constrictions assume a forwardly 

 directed curve much nearer the umbilical zone. 



Our best thanks are due to Mr. G. C. Crick for the advice which he 

 has kindly given us in the preparation of this paper. 

 EXPLANATIOJSr OF PLATE II. 

 Fuzosia curvatisulcata, sp. nov. 

 Fig. 1. — Part of a whorl, shoTving constriction and faint ribbing. 



,, 2.- — End view of same. 



,, 3. — Part of a smaller whorl, showing constriction. 



(These figures are f natui-al size.) 



,, 4. — Suture-Hne (natural size) traced from the original specimen. 



Horizon. — T\iVQm2ia—zoneoi Holaster planus : Waterworks Quarry, Marlow, Bucks. 



1 F. Stoliczka, Cretaceous Fauna of Southern India (Pal. Indica), 1865, vol. i, 

 p. 134. 2 F. Kossmat, op. cit., p. 116. 



