ANNELIDES. 601 



1. Shell with a longitudinal, lateral, suharticulated slit. 

 This includes the genus Siliquaria {Serpula anguina), the 

 characters of which remain to be determined. 



2. Shell destitute of a lateral slit. In the genus Denta- 

 Jium, the tube is open at both ends. The sides of the body 

 are furnished w ith tufts of bristles, and the posterior extre- 

 mity terminates in a radiated disk, where, probably, the 

 branchiae will be detected. In the genus Csecalium (which, 

 when instituted, Edin. Encyc. vol. vii. p. 67, I inadvertently 

 termed Caecum), the smaller end of the shell is closed. 

 Three British species, formerly included in the genus Den- 

 talium are known, viz. C. imperforatum, trachea and gla- 

 brum. The animal is unknown, 



B. Fixed or permanently attached to other bodies. 



1. Shell closed at both ends. The cover of the extremi- 

 ty corresponding with the mouth, is covered with tubular 

 elongations. There is only one genus, Penicillus, formed 

 from the Serpula penis, Lin, 



2. Shell open at the mouth. 

 a. Shell irregular. 



(a.) Operculum multivalve. This inckides the genus 

 Galeolaria of Lamark. 



(b.) Operculum simple. There are two genera. 



1, Vermilia (Lam). Shell attached throughout, with 

 the aperture round, and the margin toothed. Operculum 

 shelly. V. vermicnlaris, triquetra*^ and serrulata are na- 

 tive species. 



2. Serpula. Shell not attached throughout. Mouth 

 round, with a simple margin, S. tubularia. 



" The observations of Montagu, indicate several species to be includ- 

 ed under the name of Triquctra. — Testacca Brilannica, Supp. p. 15(>. 



