74 ZOOLOGY. 
clouded with violet, and the pallial impression curved. The older authors ~ 
placed it under Venus and Tellina. It inhabits Junk river and_ other 
rivers of west Africa near the mouth.* 
Glaucomya of Gray belongs here. Mr. Cuming found it living in the 
fresh waters of the Philippines, and it occurs fossil in the freshwater forma- 
tions of Paris. It was at first confounded with Venus. 
fum. 5. Tellinide (also named Nymphacea). In this family the cardinal 
and accessory teeth are well developed, the shells are seldom covered with 
u periostraca, the mantle is margined with very sensitive tentacular 
appendages, and closed posteriorly, the siphons are exserted, and the pallial 
impression has a deep sinus. . 
Donax (pl. 16, figs. 88, 39) has a wedge-shaped shell, truncated upon — 
the posterior slope, making this extremity. unusually short. Some authors, 
as Swainson, have mistaken the posterior for the anterior extremity, 
although the short ligament and the curve in the pallial impression should 
have prevented such an error. Donax is a genus of handsome and usually 
small shells, abundant in individuals, and living vertically in the mud at a 
trifling depth of water. A few species are found in tertiary formations. 
Capsa includes shells allied to Donax, but without accessory teeth. 
Tellina (pl. 76, fig. 44) is a genus of handsome and usually elongated 
shells with a fine nacre, often polished and radiated externally, and in some 
eases rough. The recent species are numerous, and there are a considerable 
number of fossil species in the tertiary of Europe and America. 
Blainville places Amphidesma as a section of Lucina; Latreille considers 
it the representative of a family; and Deshayes thinks it has characters 
intermediate to Mactra and Tellina, to the latter of which he surmises that 
the unknown animal is allied. : 
Fam. 6. Lucinide. This family is sometimes united to the Tellinide. 
Lucina presents some important distinguishing characters. The shell is 
suborbicular, white or pale colored ; the labial palpi are absent, the branchie 
of each side are united so as to appear single, although separable; the foot 
is vermiform, and there is a single anal siphon capable of being turned 
within itself like the finger of a glove. The branchial siphon is reduced 
to a simple perforation. The genus has numerous species, recent and fossil 
in the tertiary formations. 
Fam. 7. Veneride. This family contains the extensive genera Venus 
(pl. 76, fig. 86) and Cytherea (fig. 87), and also Arthenvs of Poli. The 
species of Venus and Cytherea being numerous, the accessory tooth which 
distinguishes the latter is found more or less developed, and as it is at times 
reduced to a mere vestige, Deshayes is inclined to consider the genus as 
* Magadesma of Bowditch was probably published in his treatise on Conchology. It was 
named Galathea by Bruguiéres, a name which has been already used. Sowerby called it 
Potamophila, and De Roissy Hyeria, a name which occurs three times in Entomology, being 
instituted by Dumeril in 1806, Fabricius in 1808, and Desvoidy in 1830. Leach used it in 
1815 in the Crustacea, and Lea in 1833 in the Mollusca. The constant use of Agassiz’ important 
and laborious Nomenciator Zootoeicus (containing 33,000 names of genera, &e.) can alone 
prevent such confusion. 
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