Protoconch

Ontogenetic torsion and protoconch form in the archaeogastropod Haliotis kamtschatkana: evolutionary implications.

The protoconch was thin and transparent, covering the entire body except the cephalic region (Fig.

In another case a capsule contained eight veligers that were adding a whorl to the protoconch, though all shells were as yet wider than long.

Protoconch elongated, smooth, shining, ~2 whorls; boundary between protoconch and teleoconch well-defined, orthocline (Fig.

megalsphere is spherical and the deuteroconch embraces the protoconch in the axial section.

Although the photographs illustrate many of the characters described, an occasional diagram would have been useful; a case in point is the spiral thread-like sculpturing of the protoconch of Radiodiscus abietum, which is diagnostic but not clearly visible in the photographs.

The first 1.75 whorls of the protoconch are smooth, after which very fine riblets develop into distinct uniform riblets by the end of 2.5 whorls.

Shell acute; fusiform with brown zigzag protoconch with calcarella* (Adelomelon s.s.) 2 --Shell globose without brown zigzag markings; apex globose or mammilliform; protoconch without calcarella Pachycymbiola) 4 2.

The smooth protoconch and nature of the ribs appear to be that of Palaeozygopleura.

One character, flattening of the protoconch, was excluded from the analysis, as possibly dependent on protoconch width (character 24).