Perisserosa guttata - its subspecies and forms

A quick "how can I tell"

There have been people who wonder about the differences between the various taxa assigned to
the beautiful and variable P. guttata (formerly Erosaria)

Here is a short comparison:

 guttata guttata  guttata guttata var. bicallosa  guttata surinensis  guttata surinensis var. bengalensis  guttata azumai
 dorsum with large and small lacunae  dorsum with small lacunae  dorsum with large but mostly blurred lacunae
 small blotch on labrum  large blotch on labrum  mostly no blotch on labrum
 Philippines  India to Thailand  China Sea
 stripes on labrum rather corarse, moving slightly towards dorsum  stripes on labrum rather coarse interrupted by white callus  stripes on labrum moving far onto dorsum  stripes on labrum finer, moving towards dorsum, but not quite that much  stripes on labrum very coarse and fewer, not moving onto dorsum, no white callus
 columellar side hardly callused  columellar side stronly callused, interrupting lines  columellar side slightly callused  columellar side very callused, but lines go across  columellar side not callused at all
 Rather large, inflated and heavy  smaller, slightly depressed, very heavy  smaller, depressed, heavy  smaller, very heavy and very depressed  larger, light weight and inflated
 basal ground color white  basal ground color yellowish  basal ground color white

guttata guttata: note the two distinct basal blotches, the absence of a labral blotch,
the large and small lacunae and the inflated shell

guttata guttata, variation bicallosa: it is smaller and depressed,
the sides are heavily callused with a white accumulation

guttata surinensis: the basal blotches are larger, the lines finer and moving up further.
Note the smaller and more numerous dorsal lacunae

guttata surinensis var. bengalensis: in this insignificant variation, the shell is more callused and broad.

guttata azumai: in the subspecies (of geographic variation) from the China Sea ,
the shell is lighter in weight, the stripes are short and coarse, and the blotch on labral side
is mostly (but not necessarily) absent. The dorsal lacunae are often small as in the one shown here,
but may be rather large, but they are mostly indistinct.

© F. Lorenz, 28.05.2004