anal valve造句

• In centipedes the telson is the rear-most body segment, posterior to the genital openings, bearing two anal valves.
• The anus is surrounded in its length by folds called anal valves, which converge at a line known as the pectinate line.
• The final segment is known as the telson and consists of a legless preanal ring, a pair of anal valves ( closeable plates around the anus ), and a small scale below the anus.
• This species can be confused with the purple sea urchin " Paracentrotus lividus ", but the latter is never really black ( though often very dark ), has more dishevelled spines of many lengths, covers itself with debris, has spines around the mouth and no anal valve, and does not live exposed on the cliffs.