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Phormostichoartus schneideri Nigrini and Caulet, 1992

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Phormostichoartus schneideri Nigrini and Caulet, n.sp. Plate 6, figures 3-6

Description: Thick-walled, smooth, cylindrical shell consisting of three segments. Cephalis approximately spherical with a well developed, cylindrical, poreless vertical tube lying along the proximal part of the thorax; few, relatively large, subcircular pores, irregular in size and arrangement. Apical spine free within the cephalis, but no apical horn. Vertical spine horizontally directed along the axis of the vertical tube; dorsal spine projects as a small thorn and lateral spines create small indentations where they meet the cephalic wall. Collar stricture indistinct.

Thorax short, truncate conical with subcircular pores, not uniform in size, usually in 3 or 4 transverse rows, 4 pores on a half equator. Lumbar stricture distinct, but not pronounced.

Abdomen consists of two parts, a proximal, somewhat inflated, section followed by a longer, approximately cylindrical, section. There is distinct break in contour between these parts, but no internal ring denoting true segmentation. Pores in transverse rows, fairly regular in size and arrangement proximally, but increasingly irregular distally. Six pores on a half equator at the widest part of the abdomen. Termination neat, consisting of a poreless band with small hyaline projections. It is not clear if this is a peristome with terminal teeth or the beginning of another row or pores.

Dimensions (based on 25 specimens): Length of cephalis 15-15 µm; of thorax 19-24 µm; of abdomen 70-120 µm. Maximum breadth of cephalis 25-29 µm; of abdomen 48-62 µm.

Distinguishing characters: This species differs from P. fistula and P. pitomorphus by having only three segments and by its lack of a well-developed peristome. It differs from P. caryoforma bye the pronounced change in contour of its abdomen and larger size.
Nigrini and Caulet 1992











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