242 W. H. Hudleston — On the YorJcshire Oolites. 



cannot think that the question of punctate structure is anything 

 more than one of status (condition of preservation). All these 

 smooth Chemnitzias are striato-punctate under certain conditions, 

 whilst there are other conditions where the feature is not shown. 

 It so happens that the specimen figured by Sowerby shows this 

 peculiarity in a very slight degree. Most of the specimens from, 

 the Dogger show it, but not all. 



In the other two zones of the Inferior Oolite in Yorkshire this 

 structure is not noticeable either in the species of Chemnitzia, or, as 

 far as my observations go, in the species of Natica, whose representa- 

 tives show it so strongly in the lower horizon. 



Description (Figures la and Ih). — Specimen from the Dogger 

 (zone 1) Peak (Blue Wyke). Leckenby Collection. 



Length (restored) 95 mm. 



Width 20 ,, 



Length of body-whorl to entire shell 28 : 100. 



Spiral angle li^-lS". 



The upper portion of the spire is so indifferently preserved that 

 the above measurements must be received with reservation. The 

 three anterior whorls are in tolerable condition, with the suture well 

 marked. The upper portion of these whorls shows a flattish belt, 

 very feebly developed, in front of which is a slight constriction and 

 then again a slight fulness, after which the whorl is again constricted 

 to meet the next suture. Eugose and wavy lines of growth, accen- 

 tuated by conditions of fossilization, are conspicuous. A fine striato- 

 punctate structure is discernible, chiefly on the penultimate whorl. 



Aperture oval, and rather small. This effect is increased by 

 thickening of the outer lip through adherence of matrix. 



(Fig. 2). — Another specimen from the Dogger. My Collection. 

 Spiral angle 15°. 



This serves to show the early stage, where the belt is but feebly 

 developed, yet increases in importance with each succeeding whorl, 

 the slight constriction of the whorl increasing pari passu. Sutures 

 clean cut out, and angular. Surface smooth, no striato-punctate 

 structure visible. 



(Fig. 3). — Another specimen from the Dogger. Bean Collection, 

 British Museum. This serves to show the youngest stage. The 

 apical whorls are flat and devoid of any varix, and the suture close, 

 I think that this is the form called " Terehra melanioides " by Bean. 



Belations and Distribution. — If we are to make a distinction ac- 

 cording to whether or no punctate structure is visible, Figs. 2 and 3 

 will represent Ch. procera, Desl. It is a point on which opinions 

 will perhaps continue to be divided for the present. 



It should be borne in mind that all these large Chemnitzias com- 

 mence with a very flat whorl. The apical whorls of Chem. Hedding- 

 tonensis are probabl}' the Chem. melanioides of Phillips. 



Chem. lineata-procera is well represented in the Dogger and 

 Millepore ; nor do I think there is any real difference in the variety 

 next to be described from the Scarborough Limestone. 



