embryonic shell造句

• Their embryonic shells are lost within the first few days after hatching.
• Nautiloids have relatively large embryonic shells, and living species lay a few large eggs.
• At the very tip of the phragmocone beneath the rostrum is an embryonic shell known as the protoconch.
• In contrast, bactritids and ammonoids produced large numbers of small eggs, each housing a small embryonic shell.
• The embryonic shell globose, flat above, of 2 whorls, narrowed toward the base and narrowly umbilicate.
• The periostracum of the embryonic shell ( inside the egg ) begin to grow in 48-hour old embryos.
• Juvenile shells show a long tower-shaped protoconch or embryonic shell of 5 whorls, which is usually lost in the adult.
• Bactritids are distinguished from the more primitive nautiloids by the small size and globular shape of the protoconch, the so-called embryonic shell.
• At the tip of the phragmocone beneath the rostrum is a tiny spherical or cuplike nodule known as the " protoconch ", the remains of the embryonic shell.
• The weight of the embryonic shell in 5-day old ( 120 hours old ) embryos a very short time before hatching, is 30.3 ?g, and the width is 500 ?m.
• To be more precise, the apex would usually be where the tip of the embryonic shell or protoconch is situated, if that is still present in the adult shell ( often it is lost or eroded away ).