Beaked larva
[this juvenile, not belonging to the pelagic molluscs, is included as it is frequently mistaken for a pteropod]
Overview
This is a shelled larval snail (not a pteropod) up to 0.1 cm long, with a semi-transparent uncoiled shell. The cross-section is round. The surface has transverse rings. The shell is long and narrow, tube-shaped, straight and not tapering towards the end. The mouth rim is not continuous as an anchor-shaped tooth projects. It lives in warm waters in the upper layers of all oceans (Beaked larva).
Taxonomic Description
Shell straight with distinct broad transverse ribs that are of equal strength over the entire shell length. The lateral sides of the shell are parallel so that the shell diameter is the same at all levels. Aperture oval with beak (Beaked larve aperture). Embryonic shell oval not sharply separated off from the teleoconch. The soft parts in the preserved specimens occupy about 2/3 of the shell volume. At the top of the body a bilobed velum, 0.1 mm long, is found in between a small footlobe. The animal is fixed obliquely to the shell by 6 columellar muscle fibres each about 0.15 mm long. The greater part of the body consists of interstitial tissues indicating that they are juvenile specimens.
Shell length 0.8 - 1.2 mm width ±0.1 mm, the relatively large embryonic shell is 0.25 mm long.
Juveniles
This is a juvenile itself.
Others
Chen (1962) pictured this species under the name Creseis chierchiae and probably did not distinguish between real Creseis chierchiae specimens and the present species. Frontier (1963b) described this species as resembling Creseis acicula given by Tokioka (1955) and as representing a yet undescribed new species. Richter (1976) stated that this species does not belong to Creseis and that it could even not belong to the Gastropoda, but no further arguments were given. Frontier (1963) considered this species, figured by Menzies (1958) to be a pteropod, probably of the genus Creseis but did not consider it to be Creseis chierchiae. McGowan (1960) places 'Beaked larva' and Creseis chierchiae together but he mentioned the differences between the two, especially with regards the embryonic shell.
Types
Not relevant.