362 
Tellinid^.- 
-MOLLUSOA.- 
-Telliniu^. 
ventricose, smooth, or concetitrically striated. Tlie 
liinge is narrow, and has in most cases two short mode- 
rately diverging cardinal teeth in each valve, and two 
elongate, smooth, compressed, lateral teeth in one 
valve, and one in the other. The species are all small, 
and are for the most part natives of cool climates. 
Tliey inhabit fresh-water lakes, ponds, streams, and 
ditches, and are generally found buried in the mud. 
The British species which have been observed are ovovi- 
viparous, the fry being hatched in the internal branchiae. 
They breed readily in confinement, and often exhibit 
when young considerable activitj^ climbing about sub- 
merged plants, and often suspending themselves by 
byssal threads. 
Family— TELLINID.^®. 
The Tellens are numerous, often remarkable for 
elegance of form, delicacy of sculpture, and beauty of 
colour. Many of them are thin, fragile, and com- 
pressed; and though a strong general resemblance may 
be observed to exist throughout the family, yet many 
modifications of form, and considerable differences in 
the structure of the hinge occur, so as to compel 
their separation into a number of distinct genera. The 
animals, however, are strikingly similar, and are parti- 
cularly noticeable for having the siphons very long 
and slender, and the foot bent so as to form a sort of 
elbow. The shell is always free, compressed, and 
regular; the hinge is never furnished with more than 
two cardinal teeth; and the lateral teeth are either one 
in each valve or are obsolete. The ligament in some 
is external, in others internal, and the pallial sinus is 
usually very large. Though the shells are often painted 
with glowing hues, yet the animals are said to be almost 
always white and colourless. One or two, as Tellina 
Gari, are used as food; and in India this latter species 
forms a favourite dish called bacassan, which old 
Kumphius extols as “ the most grateful of all kinds of 
food.” 
Genus Tellina.— This genus, as now restricted, 
has an ovate shell, oblong, or rounded posteriori}', and 
peculiarly marked with a fold or sinuosity on the 
hinder side. The species vary much, however, in 
form and appearance ; some are elongate transversely 
(see Plate 10, fig. 2, TeMma radiald ) ; others are 
oval and rough externally ; others, again, are nearly 
orbicular; one or two have one valve flat; while both 
valves in others are remarkably deep. In sculpture 
they are equally various ; some have one valve striated, 
the other plain ; others have the external surface very 
rough ; others, again, quite smooth. The hinge teeth 
are compressed; the ligament external, prominent; and 
the pallial sinus very wide and deep. The Tellens live 
in sand or sandy mud, buried beneath the surface; the 
majority at low w'ater-mark, though some occur at 
considerable depths. “ The animals have the power of 
leaping from the surface by means of their muscular 
foot” {Adams ) ; and no doubt this power is increased 
by the elbow-shaped bend in that organ. 
Genus PsAMMOBiA. — This genus (some of the species 
of which are known by the name of the “ Setting Suns”) 
have an oblong, compressed shell, slightly gaping at 
both extremities, and more or less angular at the hinder 
side. The ligament is external, prominent ; the hinge 
provided with two teeth or a single bifid tooth in one 
valve, and only one in the other ; and the pallial sinus 
is deep. Externally, they are either smooth or radiately 
striated, and the internal margin is finely crenulate. 
Genus Sanguinolauia. — This genus has an equi- 
valve, oval, compressed shell, attenuated at the hinder 
end, and gaping a little at both extremities. The 
ligament, which is external, is very conspicuous on a 
prominent thickening of the hinge margin, and the 
pallial sinus is very deep. 
Genus Semele {=Aviphidesmci ). — This genus has 
a rounded, subequilateral shell, with the beaks turned 
forwards. The hinge is provided with a short external 
ligament, a long, oblique internal cartilage, and the 
teeth are two cardinal in each valve, and distinct, elon- 
gated lateral teeth in the right valve. 
Genus Donax or Wedge-tihell . — This genus has a 
strong, more or less wedge-shaped shell, the hinder side 
being much shorter than the anterior, or as it were, 
truncated. The ligament is short, external, the hinge 
furnished with two cardinal teeth in each valve, and 
one or two lateral teeth, and the pallial sinus is wide 
and deep. The external surface is smooth, radiately 
striated or decussated, and covered with an epidermis. 
The inner margin is generally crenulated. When the 
animal moves, it does so by a succession of short leaps, 
and this peculiar mode of progression has been well 
described by Dr. Johnston as observed in the common 
Donax truncidus of our own shores. “ When it is about 
tomake a spring,” says the Doctor, “it firstly, by appro- 
priate motions of fhe foot, puts the shell on the point or 
summit, as if aware that this is the position the most 
favourable of any to avoid the resistance which the 
sand opposes to the motion. It then stretches out the 
leg as far as possible, makes it embrace a portion of the 
shell, and, by a sudden movement similar to that of a 
spring let loose, it strikes the earth with its foot and 
effects the leap.” 
Genus Ipiiigenia {=Capsa ). — This genus has a 
nearly equilateral, transverse, smootli shell, covered 
with a thin, olivaceous epidermis. The hinge is pro- 
vided with two cardinal teeth in the right valve, and 
one cardinal and two nearly obsolete lateral teeth in 
the left valve. There are only a few species known, 
and these are found in estuaries in Brazil, Central 
America, and Senegal. They bury themselves at a 
small depth in the sand, where they are said to lie with 
the posterior part upwards, to facilitate the influx of the 
water for respiration. 
Genus Galathea. — This genus has a remarkably 
thick, trigonal, wedge-shaped, smooth shell, covered 
with a smooth, olive epidermis. The umbo is generally 
eroded ; the short, external ligament is prominent and 
turned, and the hinge is thick and furnished with two 
large thick cardinal teeth in one valve and one in the 
other, and two indistinct lateral teeth. When young, 
the teeth are like those of the preceding genus, Iphi- 
genia, but as the shell enlarges in size and increases in 
thickness, the teeth increase in size and become sub- • 
divided into separate lobes. Two species are known, 
both inhabitants of the sand}' flats of the Nile and the 
