ARRANGEMENT OP THE ANNELIDES. 23 



several families ; viz. the Serpulidce, the AmphitritidcB, 

 and the Terebellidce, &c. : the latter reside in slight 

 tubes, which are buried in the sand or concealed beneath 

 stones. The AmphitritidcB are readily recognised by the 

 golden setae, arranged like the teeth of a comb, at their 

 anterior extremity. The tube of the Serpulida is cal- 

 careous and convoluted ; and the anterior extremity of 

 their body is ornamented with a coronet of appendages 

 resembling plumes disposed in the shape of a funnel. 

 They contain many genera, as Serpula, Sahella, Her- 

 mella, Pectinaria, &c. 



(20.) The Annelides MESOBRANCHiiB, which con- 

 stitute the second subdivision of the Annelides Cheto- 

 podes, are distinguished by the body extending beyond 

 the oral aperture ; and it is usually terminated by a dis- 

 tinct head, frequently furnished with eyes and maxillae ; 

 and they have either no appendages, or these are placed 

 along the whole course of the body. They are separated 

 into three families ; viz. the Terricoles, the Arenicoles, 

 and the Errantes, or Cephalotce. The first of these have 

 no dermal appendages ; and have neither a very distinct 

 head, eyes, antennse, nor maxillse ; their body is cylin- 

 drical, attenuated at both extremities, and furnished 

 with several rows of setae, which serve them instead of 

 legs ; and they live either in humid earth, or in the 

 mud. The Lumhricus, or earth-worm, is the best 

 known example of this group, which consists of three 

 tribes, — the Thalassamenidce, the Lumhricidce, and the 

 Cli/menidcB. The first contains the genera Thalassema 

 and Sternapsis ; the second, iVa'is, Tubi/ex and Lumbri- 

 cus ; and the third contains Ciymene ; which last makes 

 an approach to the Tubicoles, on account of its fragile 

 tube, formed of grains of sand and particles of shells, 

 although its structural peculiarities agree better with 

 this family. 



(21.) The second family, the Arenicoles, consisting 

 of the genera Arenicola and Chetoptera, have many 

 characters in common with the preceding : these have, 



c 4) 



