NATURAL HISTORY. 
77 
GALLERY.] 
this genus is club-shaped, contorted, opaque, and closed at the end ; 
they live crowded together in woody fruits, and have been confounded 
with Fistulunce. 
The family of Gastroch^nadje have animals very similar to the 
former; the valves are thin, gaping in front, and united by a narrow 
ligament with a thin marginal cartilage. They live inclosed or some¬ 
times imbedded in the substance of a shelly tube, which is formed by 
the animal to protect its elongated and partly naked body from the 
roughness of the sand, or the rock in the holes of which they reside! 
The animal is provided with a series of filaments in front, which it 
emits to ascertain what is in its neighbourhood, and for the protection 
of which it forms tubes that serve as anchors to keep the tube of the 
body in its place ; and when it requires to enlarge its tubular dwelling, 
it adds new matter to the outer or hinder extremity of the tube, having 
previously absorbed any of the old tube that may be in its way. When 
this is not the case, the expanded mouth of the old tube forms ruffles 
on the tube beneath the last formed aperture. In Aspergillum both 
the valves are imbedded in the lower part of the tube, so that only their 
umbones can be seen on the outer side. In Aspergillum the lower end 
of the tube is regularly convex, pierced with a central slit and tubular 
holes, and surrounded with a regular fringe of tubes, which are some¬ 
times branched at the end, and in Fcegia the lower end is irregular, 
with scattered tubes, and destitute of any fringe. In Clavagella one 
valve is imbedded and the other is free, while in Fistulana and Gastro - 
chcena both the valves are regular and free; in the former the tube is 
regular and club-shaped, and in the latter it is irregular, distorted, and 
attached to the bodies in which it is imbedded with only the smaller 
end free. The Bryopoe , which are only known in a fossil state, 
appear to have lived in sand like the Aspergillum , for the tubes are of 
a regular club-shape, with a fringe of small tubes round the disk. 
The genus Furcella may either belong to this or the former family, for 
the animal and valves are not known, the tubes are large and thick, formed 
of prismatic crystals, thinner and enlarged at the base ; the cavity of the 
upper end is divided into two distinct tubes, which are sometimes 
elongated into separate diverging tubes. 
The family of Solenid^ have a very elongate club-shaped foot 
and elongate subcylindrical valves gaping at each end; the hinge is 
formed by two or three compressed teeth in each valve, the hinder of 
which is bifid, and the cartilages are external, linear, and supported on 
a large very prominent pad or fulcrum. In Solen and Ensis , the foot 
is club-shaped, and the syphons are short and united. In Pharus, the 
foot is long with a dilated end, and the syphons are elongate and 
separate. In Solecurtus the foot is ovate, compressed, very large, and 
the syphons very long, united together beneath, and distinct at the top, 
where they often separate into rings when irritated. In Cultellus the 
foot is thick and pointed, and the two syphons are separate nearly to 
the base. In several the periostraca is hard and produced beyond the 
margin ; in Glycimeris it is much produced, very thick and black, and 
the syphons are united. 
Ctenoconcha, which has many characters in common with the Solens, 
has the teeth like Nucula , but it has an external cartilage. 
The family of Anatinidje have a broad compressed foot; the 
