ANNELIDES. 599 



and sides are imbedded. One species, the Balanus spon- 

 giosus of Montagu, is a native of the British seas. 



Fcumily 2. — The valves of the shell are only four in 

 number, 



1. Creusia. The base is funnel-shaped. The lateral 

 valves of the lid are united. The C. spinidosa of Dr 

 Leach is the type of the genus. It is imbedded in the 

 substance of Madrepores. 



2. CoNiA. The shelly base conforms to the substance 

 to which it is attached. The lateral valves of the lid are 

 separate. The C. porosa is the type of the genus. 



3. Clisia. The base of the shell is spread on the sur- 

 face of the bodies to which it is attached. The lateral 

 valves of the lid are united. The Balanus striatus of Bri- 

 tish writers is the type of the genus. An imperfect repre- 

 sentation of the animal is given by Cord in er, in his 

 " Remarkable Ruins^ plate inscribed " Aggregate of Co- 

 rals." 



Familrj 2. — The shell is undivided in the only genus of 

 this family which is known, termed Pyrgoma. 



Section II. — As^elides. 



Shell not multivalvular, or wanting. 



The body of the Annelides is of a lengthened form, 

 bearing, more or less, a resemblance to the common Earth- 

 worm, and, like it, divided into numerous rings. The skin 

 is furnished in many genera with different kinds of appen- 

 dices. In some, it is protected by a shell secreted by the 

 animal. In others, particles of sand or mud are cemented 

 by mucus, in the form of a convenient dwelling, which the 

 inhabitant never quits. The head, in a few genera, cannot 

 be distinguished i'rom the opposite extremity. In general, 

 however, it is marked by the antennae, the tentacula, and 

 eyes. The sides of the body are in some species naked, and 



