112 HYATT ON THE TERTIARY SPECIES 



Line d, figs. 1-7 PI. crescens. Fig. 2 line d shows a specimen of the young, which at a very early age 

 begins to show the compressed form of the whorl, which distinguishes the adult of PL crescens. In fact the 

 three young specimens on this line form a series in this respect, fig. 2 being the most compressed, fig. 6 next, 

 and fig. 4 the least, although figs. 2 and 4 are of the same age and fig. 6 a little older. The adults of all of 

 the three would have been about equally compressed in form. 



Plate VI. 



Magnified 5K diameters. 



Line a, figs. 1-3 PI. levis from Undorf, 4-7 PI. "^S!" {=reverte?is Hilg.). 



Line b, figs 1-6 PL "^■'^"^ {—revertens Hilg.), somewhat stouter than the normal forms of PL levis, even 

 in the young, fig. 5. 



Line c, figs. 1-5 PL oxystomus with extremely stout whorls even in the young. In this variety the young 

 are.very similar to the rotundatus-like young of PL trochiformis, see pi. 2, line o, figs. 1-14, line p, figs. 1-8. 

 They, however, are distinct in the aspect of the upper umbilicus, in the oarinations and shell, and outline of 

 the opening of the whorl, especially in the younger stages. Compare also figures on lines, o and p, pi. 3, with 

 figures of young of PL oxystomus var. cochleatus, pi. 3, line 1, figs. 4-11, which also have extremely stout 

 whorls in the young. Fig. 6 is a fine specimen of the transition from the normal variety to the turretted 

 form, variety cochleatus of PL oxystomus?- 



,Line d, fig. 1 PL oxystomus ysw cochleatus, full grown shell,^ figs. 2-4 PL oxystomus, normal variety, 

 showing the identity of a young shell, fig. 4, with a shell of the same size of P^. levis, from Undorf. 



Line e, fig. 1 PL supremus var. turritus, figs. 2-4 PL suprem,us. 



Plate VII.^ 



Magnified 4 diameters. 



Line a, figs. 1-2 PL levis, Undorf. Figs. 3-5 are deef)ly umbilicated forms of PL Steinheimensis which 

 are similar to fig. 1 in this respect and in the form of the whorls. Fig. 6, PL levis, Undorf, to compare with 

 figs. 7-9 PL Steinheimensis, adult and young with a similar form of whorl. Fig. 10 an unusually turbinate 

 form of PL tenuis. 



Line b, figs. 1-2 PL Steinheimensis for comparison with figs. 3-4 PL lens, Umlorf. Fig. 5 PL Steinheim- 

 ensis with sub-angular outer whorl for comparison with fig. 6 PL levis, Undorf. Figs. 7, 8 PL Steinheimensis, 

 younger stages of same variety as fig. 5. 



Line c, figs. 1-3 PL Steinheimensis with very slight unsymmetrieal and cylindrical whorls, figs. 4, 5 PL 

 Stei?iheimennis normal variety (see specimens) with cylindrical whorls, figs. 6, 7, normal variety with unsym- 

 metrieal whorls and a deeper, narrower umbilicus on the lower side than in the preceding. Fig. 8 PL Stein 

 heimensis var. aequiunibilicatus ? 



Line d, figs. 1-6 specimens of PL /Steinheimensis with stouter whorls transitional to those of line e. Fig. 

 7 PL tenuis, from the rocks of the Upper Tier of the Cloister Ridge. This has young like the adult of PI. 

 Stein/ieimensis. 



Line e, fig. 1 PL Steinheimensis with an extremely turbinate tendency expressed in the last whorl. Figs. 

 2-4 are large fine specimens of the normal unsymmetrieal varieties, figs. 5-7, are PI. stMei!Z,ms, for comparison 

 with these and others below, for example compare the umbilicus of fig. 7, with fig. 6, line c. 



Line f, figs. 1-3 PL stedhdmenms, somowhat more advanced stage of transition, figs. 4-7 PL tenuis. 



Line g, I 'I. tenuis. 



Line h, PL discoideus, figs. 1-4 flatter variety with acute carinations, figs. 5-7 stouter varieties with gener- 

 ally less acute carinations. 



Line i, PL discoideus with rotundatus-like young, showing transitions to the varieties of PL trochiformis 

 having similar young. 



' See in this connection remarks on page 70. s See for discussion of figures on this plate, p. 83. 



^ This shell has a much shallower umbilicus than the one 

 figured on pi. 9, fig. 11, and described on p. 12. 



