ZOOLOGY. 591 



aperture at the anal extremity. They correspond to the 

 Physaliae. 



Their tegument is a perfect muscular tunic, consisting 

 of several longitudinal bands, which pursue a downward 

 course upon its internal surface ; in other respects being 

 transversely corrugated and full of papilla?, partly replete 

 with hollow podoidal filaments, which by the injection 

 of water into them are elongated ; thus, they present a 

 resemblance to the Medusae. 



Fam. 8. Beroeal Worms, Echini. 



Are at bottom Holothuriae with ossified tegument, or 

 Asteriadae with shortened rays. 



The Echini have an anus, pretty like that of the 

 Holothuriae, and also similar feet, which are protruded 

 in a similar manner through apertures in the shell. 

 The dental wreath surrounding the mouth is a complete 

 bony framework, which has been called, on account of 

 its form, " Laterna Aristotelis," and bears a considerable 

 resemblance to the valves of the Balani, the antetypes 

 in general of the Echini, just as these are of the Opossum 

 Shrimps. 



Fam. 9. Medusa! Worms, Aster iada. 



Body stelliform, consisting of bony rings ; contains a 

 free multilobular intestine with blood-vessels and branchiae; 

 several ovaria; it would appear that they are without 

 male parts. 



Herebelongthe Encrinites, Pentacrinites, and Asteriadae 

 proper. Around the mouth of the Encrinites and Peu- 

 tacrinites stand long, ramified, and likewise articulated 

 tentacula, which remind us of the arms of the Medusae 

 and Cephalopoda. 



Fundamentally too, in the Star-fishes, the disk only is 

 the body proper, and the rays are the tentacula, which, 

 being monstrously developed, surround the mouth ; what 

 have been called pedicles upon these, represent the suckers 

 of the Sepiae. 



