Mr. Broderip and Mr. G. B. Sowerby on Mollusca. 47 
Having thus endeavoured to shew the necessity of establishing a new 
genus at least, if not a new family, let us proceed to describe the animal. 
There were four specimens, one of which was sacrificed to the inquiry ; 
but decomposition was so far advanced that the ovaries and other viscera 
were nearly reduced to a shapeless pulp, and we could only trace those 
parts of the internal structure, which we proceed to lay before our 
readers.* The mantle appears to adhere only to the orifices, each of 
which consists of six triangular valvules. Each valvule is furnished 
with a set of muscular fibres, adhering at one end to the inner surface of 
the tunic (not of the mantle) and at the other ‘extremity to a small. pa- 
pillary process on the valvule. These muscles appear to be the agents for 
opening and shutting the valvules. Besides this set of muscular fibres 
and within them there is another set, which passes laterally from one 
papilla to another, forming a sphincter, the base of which is hexagonal. 
[Tas. Ill. fig. 6.] There are other strong subcutaneous muscular fibres, 
passing from the edge of the upper part of the tunic to that of the lower, 
and also from the edge of each of the coriaceous plates which form the 
upper surface. These appear to be intended to give the animal the power 
of dilatation and contraction. Externally, the animal is of an oblong 
cup-shape, adhering by coriaceous processes from the lower part of the 
cup. The upper surface, which is flat, consists of eight coriaceous, 
somewhat horny, angular plates. One of these is placed between the 
two orifices, and, in four specimens which were examined, this was of an 
hexagonal shape, the sides coming in contact with the orificial valvules 
being lunated. The plates are so disposed that the branchial orifice is 
surrounded by three plates, and the anal orifice by four, besides that 
which is intermediate and abuts upon both. The three plates near the 
branchial orifice are much larger than the four which are near to the anal 
orifice. Each of the plates is marked with three or four elevated strie, 
parallel to the sides of the plate, and near to them, leaving an area in 
* The decomposition, which prevented any thing like an accurate demon- 
stration of the ovaries and other viscera, was, apparently, occasioned by the 
spirit in which the specimen was preserved not having sufficiently penetrated 
to the internal parts. This is mentioned, in order to draw the attention of col- 
lectors to the necessity of puncturing the external integuments, muscular coats, 
&e. of such animals as are plunged entire into spirit, in order that it may 
reach and preserve the viscera. 
