. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. BASCII : FRESHWATER LIMPET SNAILS 439 County. The form appears to be a local variant, perhaps de- veloped as a result of genetic drift in a circumscribed area. The second recognizable form is not so clearly defined as is var. hcndersoni. This is Fcrrissia fragilis var. sJiimckii, and differs from the typical fragilis in its concave lateral slopes. Such a "pinched-in" appearance has been found in several pop- ulations, particularly from the north-central area, but I am not certain whether the growth form indi
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. BASCII : FRESHWATER LIMPET SNAILS 439 County. The form appears to be a local variant, perhaps de- veloped as a result of genetic drift in a circumscribed area. The second recognizable form is not so clearly defined as is var. hcndersoni. This is Fcrrissia fragilis var. sJiimckii, and differs from the typical fragilis in its concave lateral slopes. Such a "pinched-in" appearance has been found in several pop- ulations, particularly from the north-central area, but I am not certain whether the growth form indicates a genetic or an ecological difference from otliei* populations of F. fragilis. POPULATIONS OF Ferriscia fragilis N Corolino I Kansas N. Carolina 2 Washington Oregon ; 2. A COMPARISON OF SHELL PROPORTIONS NON SEPTATE INDIVIDUALS ONLY. i:6 RATIO length width T5" N. Carolina I Kansas N. Carolina 2 Washington Oregon .205 .20 .267 .3'0 .333 .40 RATIO hBlght length .406 .465 :g5" Fig. 18. Comparison of proportions of five populations of Fcrrissia fra- gilis. Eanges, means, and standard deviations indicated as on Figure 17. Number of specimens measured same as N for non-septate individuals on Figure 17. Upper group, ratio of length/width (measure of width) ; lower figure, ratio of height/length (measure of elevation). Note the apparent absence of any geographical 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 Comparative Zoology. Cambridge, Mass. : The Museum
Size: 2758px × 906px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorharvarduniversity, bookcentury1900, booksubjectzoology
