102 CARDIAD #. 
meter, with the animals of the C. nodosum, that they are 
identical. 
If it had been our practice to generalize, the smgular same- 
ness of the organs of this genus would have authorized a 
departure from the plan of detailig the specialties of every 
case: the present work is not intended to be subjected to the 
dull and heavy labour of bemg doggedly read through con- 
secutively ; we consider it one of particular reference, and 
think that we have done good service to the reader in stating 
the specialties at length m nearly every case. 
C. NoRvEGicuM, Spengler. 
C. norvegicum, Brit. Moll. u. p. 35, pl. 31. f. 1,2; (animal) pl. N. f. 1. 
C. levigatum, Auctorum. 
Animal thick, suboval, elongated, the vertical measure 
exceeding the transverse; the mantle is closed throughout 
the posterior range, and at its lower part forms two short 
siphons united at their bases and divergent at the extremities, 
of a pale yellow, marked with flake-white spots and lines; the 
branchial tube is rather the shorter, but of greater diameter, 
and is rarely extended more than half an inch; its orifice is 
circled with twenty long yellowish-white cirrhi, having dull 
red-brown markings around their bases; the anal siphon is 
simple, and has the usual retractile valve, which is marked on 
the lower and upper surface with a famt red-brown line, and 
points of the same colour at the termination. The siphons 
and the posterior range are clothed with thick-set pale reddish- 
brown and pale yellow curved filaments. The mantle, from 
the pot where the filaments terminate, is simple and open, 
with its outer and inner margin of a flesh colour, and affords 
a passage to a long, powerful, geniculated, cylindrical foot, 
that has a pomted termination; its substance is rigid, and, 
except the white point, of a red flesh colour, which the slightest 
touch removes and shows the white ground; it is longer than 
the greatest measure of the shell, and its epidermis appears 
shagreened and marked with anastomosing fine lines. There 
are on each side a pair of pale brown suboval branchie, with 
the margins of a deeper brown; the wpper one is considerably 
