no 
SERPULA. 
A. Flexuous, irregular, and adhering’. (Plate 
XXII. Fig. 2.) 
B. Assuming a certain form, detached. (Fig. 3.) 
Shell univalve, tubular, gradually tapering, often 
interrupted by imperforate partitions at irregular 
distances. Frequently closed at one end. 
By constituting two divisions of this genus, and 
omitting the character of adherence in the generic 
description of Linnaeus, we legally include a great 
variety of shells, which, without this alteration, 
were inconsistent with the definition. Many spe- 
cies which should rank in the first division have a 
great appearance of regularity in their structure, 
and yet, strictly speaking, are irregular. The end 
is twdsted, sometimes the whole shell, into a spiral 
form, much in the same manner in all the indivi- 
duals of the species ; but there is no fixed number 
of circumvolutions, nor any symptom of the animal 
being directed by an invariable law, as in turbi- 
nated and other genera. 
