. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 482 BitUctin Museum of Comparative Zoology, Vol 138, No. 7 bermudensis west zonatus east zonatus SG - sieglindae siegmundi H. fasoiti SH Figure 22. Values for differential growth ratio in P. berrriudensis displayed in phylogenetic framework. Cited are means of mean sample values. Formational symbols as in Figure 21. during the fourth and fifth whorl of non- paedomorphs are so delayed in appear- ance that they never form in paedomorphs. 2. Adaptive si^nificonce. There is an interesting correlati
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 482 BitUctin Museum of Comparative Zoology, Vol 138, No. 7 bermudensis west zonatus east zonatus SG - sieglindae siegmundi H. fasoiti SH Figure 22. Values for differential growth ratio in P. berrriudensis displayed in phylogenetic framework. Cited are means of mean sample values. Formational symbols as in Figure 21. during the fourth and fifth whorl of non- paedomorphs are so delayed in appear- ance that they never form in paedomorphs. 2. Adaptive si^nificonce. There is an interesting correlation between the inci- dence of paedomorphosis and depositional environment: a) Paedomorphosis is most advanced in subspecies originating in red soils. P. h. fasoiti and P. h. bermiidensis never possess a callus and rarely (with the exception of some Hving P. h. hcnntidensis) develop band 1 or 2. b) Paedomorphosis is less pronounced in subspecies originating in unindurated zones. Bands 1 and 2 are slightly delayed but usually form in P. I). sicgimiiKli and P. h. siciijindac- a callus is weakly de- veloped in both subspecies. c) Paedomorphs never originate in eolian- ites. (P. h. bermudensis, living in iso- lation, survived the period of Southampton dune building, but its geographic sepa- ration from competition renders an assess- ment of its relative adaptability to such an environment impossible). Red soil conditions seem to favor paedo- morphosis; moreover, as will be discussed in the next chapter, both P. bermudensis zonatus and P. nelsoni tend to have thinner shells in Shore Hills and St. George's times. This may suggest that paedomorphosis served as one pathway to the attainment of a thinner shell, which would have been. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Compara
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