3G2 



Tklunid^.- 



-MOLLUSCA.- 



-Telutsidje. 



ventricose, smooth, or concentrically striaterl. Tlie 

 liingo ia narrow, and has in most cases two short mode- 

 lately 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. 

 They inhabit fresh-water lakes, ponds, streams, and 

 ditches, and are generally found buried in the mnd. 

 The British species which have been observed are ovovi- 

 viparoua, the fry being hatched in the internal branchiae. 

 They breed readily in conlineinent, and often exhibit 

 when young considerable activity, climbing about sub- 

 merged plants, and often suspending themselves by 

 byssal threads. 



FAMii-Y-TELLINIDiE. 



The Tellons 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 njay 

 be observed to exist throughout the fiimily, yet many 

 modilications 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 alwa^'s free, compressed, and 

 regular; the hinge is never furnished with more than 

 two cardhial teeth; and the lateral teeth are either one 

 in each valve or are obsolete. Tlie 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 colouriess. One or two, as Tellina 

 Gari, are used as food; and in India this latter species 

 forms a favourite dish called bacassan, which old 

 Rumphius extols as " the most grateful of all kinds of 

 food." 



Gi;nus Tellixa. — This genns, as now restricted, 

 has an ovate shell, oblong, or rounded posteriorly, 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, TelUm radiata); 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 rauil, buried beneath the surface; the 

 majnrity at low water-mark, though some occur at 

 considerable depths. " The animals have the power of 

 1 'aping from the surface by means of their muscular 

 foLt" {Adams); and no doubt this power is increased 

 by the elbow- shaped bend in that organ. 



n ENus PsAMMOBi A.— This genus (some of the species 

 ofwliichare 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 tlie other ; and the pallial sinus 

 is deep. Externally, they are either smooth or radiately 

 striated, and the internal margin is finely crcnulate. 



Genus Sanguinolaria. — This genus has an cqui- 

 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 (^^^Amjihidrsmn). — This genus has 

 a rounded, snbequilateral shell, with the beaks turned 

 forwards. The hinge is provided with a shoit 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 Wedrje-shell. — 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. " '\\'hcn it is about 

 to make a spring," says the Doctor, " it firstly, by appro- 

 priate motions of the foot, puts the shell on the point or 

 summit, as if aware that this is the position the most 

 favourable of any to avoid tlie resistance which the 

 sand opposes to tlie 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, smooth 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 Galatiiea. — 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 tlie 

 other, and two indistinct lateral teeth. When young, 

 the teeth are like those of the preceding genus, Iphi- 

 gcvi'a, 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 sandy flats of the Nile and the 



