CHAPTER XI THE LOGARITHMIC SPIRAL

and which is repôÙreôÙsented in Fig. 267. By means of this litôÙtle inôÙstruôÙment, the apical angle of the turôÙbiôÙnate shell was imôÙmeôÙdiateôÙly read off, and could then be used as a speôÙciôÙfic and diagôÙnosôÙtic charôÙacter. By keepôÙing one limb of the proôÙtracôÙtor parallel to the side of the cone while the other was brought into line with the suôÙture beôÙtween two adôÙjaôÙcent whorls, another specific angle, the 〜sutural angle,〝 could in like manôÙner be reôÙcorded. And, by the