OF PLANORBIS AT STEINHEIM. 113 



Plate VIII. 



Jlngiiified 4 diameters. 



Line n, fig. 1 PI. Steinheimensis, same as fig. 13, line Ii, pi. 1, an aged specimen of extraordinary size, show- 

 ing tlie deflection and contraction of the last formed or oldest part of the outer whorl ; fig. 2 PL Steinheim- 

 ensis, also very large and beginning to sliow senile changes, same as fig. 18, line f, pi. 1. Figs. 3-5 PL 

 oxystomus; fig. 3 has the spiral deflected as the result of a wound, possibly also in part as the result of old 

 age ; figs. 4—5 are probably both distorted solely by senile or geratologous metamorjihoses. 



Line b, figs. 1-6 PL ""^S"'" (=revertens, Ililg.); figs. 1 and 6 are normal forms with spiral deflection probably 

 due to old age ; fig. 2 shows a cicatrix which has produced a precisely similar effect upon the size and direc- 

 tion of the last part of the last whorl ; fig. 3, probably distorted fi-om some normal disease or old age ; figs. 

 4, 5 are undoubtedly weak or diseased specimens in which the spiral is very greatly deflected as in PL denw- 

 datus} 



Line c, figs. 1-6 PL "'4",:*'-' These specimens are all distorted ajiparently from the. results of wounds or in- 

 juries received during the building of the last whorl. 



Line d, figs. 1-4 PL supremus ; all are more or less deflected, and the striae enlarged as tlie result of geratol- 

 ogous changes.'' 



Line e, figs. 1-3 PL trochiformis, fig. 1 shows a deflected spiral probably due to disease. Fig. 2 is a front 

 view of fig. 10, line r, pi. 2. Tlie distortion or deflection of the whorl is evidently caused by the ago and 

 perhaps also, diseased condition of the specimen, as maybe seen from the enlarged stiiae and thickened shell. 

 Fig. 3 is distorted on account of a severe wound.' 



Plate IX. 



Magnified 4 diameters. 



Figs. 1-7 Fourth Series showing transformations from PL levis var. ■''*'''S^™™ Undor^ fig. l(:=ficr. 1, line a, 

 ])1. 7), to PL trochiformis fig. 7. Fig. 2 PL Steinheimensis, 3 PL smSZiu^, 4 PL tenuis, 5 PL discoideus, 6 



TJJ trochiformis 



Figs. 8-11 Tkird Series. shovf'ins^ transformation from PL levis var. '""S;"" Undorf, fig. 8 (=fig. 1 pi. 6), to 

 PL suprernusva.i: turritus, fig. 11. Fig. 9 tliough spoken of in tlie text p. 10 and elsewhere as PL oxystomus, 

 is really a sjiecimen of revertens Hilg.= PL "^i^.',"" out of the Sand Pits, Steinheim, and ought to have been 

 supplemented by a figure of true PL oxystomus such as fig. 1, line c, pi. 6, but this i)late was already finished 

 before I became aware of the need of another figure. Fig. 10, PL supj-cmus, is the flat and sulcated variety 

 of this species. 



Figs. 12-15 Second Series showing transformations from PL levis var. ';;"," Undorf, fig. 12 (=fi<4. 1 pi. 5), 

 to PL crescens, trochiform variety, fig. 15. 



Fig. 13 PL "p"^^ The gap here which should have been filled by a figure of PLjxinjus was left unfilled 

 purposely on account of the number of figures necessary, see pi. 5, lines b, c. Fig. 14, PL crescens, normal 

 variety. 



Figs. 16-28 Mrst Series, figs. 16-20, third sub-series includes PL levis var. ""^.g"" Undorf, fig. 16 ( = fig. 2, 

 line a, pi. 7), PL "'l"'t'" fig- 17, also PI. minutus, fig. 18, wliich has cylindrical whorls showing one of the tran- 

 sition forms from PL "£,'^5"" to the normal PL minutus, fig. 21 at the base of tlie next sub-series,* also fig. 19, 

 true PL triquetrus, and fig. 20, /-"/. triquctrus var. turbinatus. 



Figs. 21-24, second sub-series includes PL minutus, fig. 21, normal smooth form, which leads into PL 

 ^mi^,tm" figs. 22, 23, and PL mitiutus var. distortus, fig. 24. The intermediate forms, etc., are given on pi. 4 

 and described in the text on pages 59 to 66. 



'See also description on p. 13, of other forms, and discus- ^Compare, also, fig. II, line s, pi. 2. 



sion on pp. 1.5, 1 7. « * The transition forms from PL minutus to PL triquetrus are 



^Compare, also, pi. 3, figs. 1-2, line n, 5, G, line g, 4, line photographed on PI. 4. 

 h; pi, 2. figs. 2, 3, line h, fig. 6, line i. 



