203 
SERPULA tetragona. 
TAB. DXCI X.—Jigs. 1. & 2. 
Spec. Char. Tube very long and narrow; free for 
a great part of its length ; externally four- 
sided, with prominent angles; aperture round. 
About one line in diameter and several inches long, va- 
riously curved ; the sides are equal, nearly flat. 
This square Serpula is very abundant in blocks of 
marl that have been removed from the oolite, and scat- 
tered over various parts of the country. Our specimens 
are from Suffolk, and contain also Avicula inequivalvis, 
a Cardium, and Astarte elegans. 
Fig. 2. represents a variety probably of the same 
species in Cornbrash Limestone, from Bedfordshire. 
Serpula quadrangularis of Lamarck is probably a dis- 
tinct species, perhaps even a Vermetus. 
SERPULA rustica. 
TAB. DXCI X.—fig. 3. 
Spec. Char. Tube externally four-angled, angles 
obtuse ; as the tube increases, the angles are 
variously bent and interrupted, at length be- 
coming irregular convexities arranged about 
a cylindrical tube. 
Nearly two lines in diameter and almost straight. The 
aperture is circular with a sharp edge. 
Found in a light-coloured marl belonging to the Upper 
Greensand, at East Weare Bay, by H.H.Goodhall, Esq., 
in whose cabinet the specimen remains. 
