APODA. 471 



These animals are found in the sands of the sea, like the Arenicolae and 

 Thalassemae, and like them are used as bait by the fishermen. 



BONELUA, Rolando. 



Here the body is oval and furnished with a proboscis, formed of a double 

 lamina, susceptible of great elongation and forked at the extremity. The anus 

 is at the opposite extremity of the body. The intestine is very long and 

 frequently flexed, and near the anus we observe two ramified organs which 

 may serve for respiration. The ova are contained in an oblong sac opening 

 near the base of the proboscis. The Bonelliae h've at a considerable depth in 

 sand, extending their proboscis to the water and even to the air above its 

 surface when the tide is low. 



THALASSEMA, Cuvier, 



Where the body is oval or oblong and the proboscis in the form of a doubled 

 lamina or bowl of a spoon, but not forked. The intestinal canal resembles 

 that of the Bonelliae. They have but one abdominal thread. 

 The Thalassemse are divided into 



THALASSEMA proper, 



Where these two hooks are placed far forwards, and the posterior extremity is 

 destitute of setae; and 



ECHIURUS, 



Where the posterior extremity is furnished with transverse ranges of setae. 



STEH.NASPIS, OWo, 



Where, in addition to the setae of the Echiuri, we observe anteriorly a 

 slightly corneous disk surrounded with cilia. 



CLASS II. 

 ENTOZOA, Rudolphi. 



THE Entozoa or Intestinal Worms are remarkable, because the 

 greater number inhabit the interior of other animals, and there only 

 can propagate. There is scarcely a single animal that is not the 

 domicil of several kinds, and those which are observed in one species 

 are very rarely found in others. They not only inhabit the alimen- 

 tary canal and the ducts that empty into it, such as the hepatic vessels, 



