OF PLANORBIS AT STEINHEIM. 35 



Eight of the specimens have exactly the form and characteristics described and figured 

 by Sandberger. PI. oJjftitn.ua is represented by one full-grown specimen, with rounder 

 whorls in the young, and only the outer whorl angulated. This leads into one full-grown 

 specimen exactly identical with Klein's figure of PI. levis, with whorls somewhat flatter 

 on the upper side, always rounded externally, and slightly stouter, so that the umbilicus is 

 deeper. This last is supplemented by one in which the whorls become still stouter, and the 

 umbilici on both sides perceptibly deeper, which is absolutely identical with PL oxystomus 

 in the general aspect and characteristic outline of the whorl, but differs slightly in the 

 more open character of the lower umbilicus. 



Two young specimens were until a late period of growth absolutely identical with PI. 

 Steinhemensis, var. ceequiumbilicatus, and one acquires an angular outer whorl when 

 not quite half grown. This one and the PL levis forms with angular outer whorls in the 

 adults cannot be distinguished from the typical specimens of PL ""'fe"'^, part of parvus of 

 Hilgendorf, such as are figured on pi. 3, line k, fig. 1-4, and many others, which a 

 reexamination of my Cloister Pit material has brought to light. The full-grown specimen 

 described as having only the outer whorl angular, is not distinguishable in any way from 

 the young shells described as transition forms between var. parvus and the Steinheimensis 

 forms of the pits. The specimens mentioned as identical with Klein's figure and the one 

 described similar to oxystomus, can be in no way separated from PL oxystomus, especially 

 forms which can be readily picked out of any large number from formation m, of the 

 Cloister Pit. In fact, these specimens show conclusively that PL Steinheimensis, PL oxys- 

 tomus, etc., are varieties of PL levis, and explain the confusion of characteristics which must 

 necessarily result as long as this is not recognized. All the gaps were not filled in the 

 pits with intermediate forms, which would be so considered by an exacting judge opposed 

 to all theoretical views of the transmutations of specific forms. This failure is here accoun- 

 ted for, and the gaps closed up by the forms found in the rocks of the Lower Steinheim 

 Period, and the more ancient Tertiaries. 



Other specimens, with rounded outer whorls, are not infrequent in the Coarse Limestone, 

 which the receipt of Prof Sandberger's specimens of PL levis have enabled me to identify 

 as precisely similar to the stouter forms of the PL '"^^et'T"'. No specimens were found 

 which could be said to have whorls identical in all respects with the angular whorls of PL 

 levis, figured by Sandberger. Gillia utriculosa was also found. 



Fraas' description states that the Coarse Limestone passes into regularly stratified fine 

 grained limestone, his " Valvaten-Kalk," which I have called Oxystomus Limestone, to 

 accord with the views taken here of the afl&nities of the fossils. 



This contains according to Prof Fraas' account of this locality only the discoidal forms 

 found in the oldest layers of the Pits. " Die Valvaten gehoren der neideren, flachen Form 

 an, die in der Sandgrube von Steinheim im unteren, altesten Lager sich finden." 



The specimens of rock hammered out by me and apparently in place contained 

 specimens of PL levis, y&r. parvus Hilg., PL "TT"*, and PL oxystomus with their young. 

 Pupa antiqua and Gillia utriculosa were also found, but were rare. Remains of fishes were 

 frequent as described by Prof Fraas, but all fossils were less abundant than in the surface 

 limestones next to be described. 



