CONCHOLOGY. 13 



D. ehurneum. The Ivory Tooth Shell. 

 Species of a reddish or pale yellow colour, with the lip 

 frequently tinged with orange or pink. 



FAMILY III. 



Amphitrit^a. Four genera. 



The similarity of the four genera comprising this family 

 is such, that it was thought sufficient to give only one type 

 (the sabellaria crassissima), as the student may easily recog- 

 nise the others. 



1. Fectinaria. Two species. 



A membranous or papyraceous tube, in the form of a re- 

 versed cone ; unfixed ; exterior covered with sandy adhe- 

 sions. 



Fectinaria Belgica. Fectinaria capensis. 



P. Belgica. The Belgic Fectinaria. 



Tube inversely conic, membranous, and covered with sand. 



2. Sabellaria. Two species. 



The covering of the animal belonging to this genus is 

 composed of fragments and particles of marine substances, 

 adhering to a tubular membrane ; some are detached and 

 others are fixed. The tubes are cellular at the base, and the 

 orifice expanded. 



Sabellaria alveolata. Sabellaria crassissima. 



(S. alveolata. The Honeycomb Sabellaria. 



Consists of numerous parallel tubes, nearly straight, com- 

 municating by an aperture, forming when in mass the ap- 

 pearance of a honeycomb ; it adheres to rocks in clusters. 



S. crassissima. The very thick or strong Sabellaria. 

 PI. 33, fig. 2. 



Species incrusted with small stones ; sometimes found 

 thick and of a large size. 



