The first five of these genera have one or two lateral teeth, the remaining two have none.
4. Tellina. The Tellen. Fifty-four species.
This genus differs but little from the Donax; its species are numerous, especially in the seas of hot countries; they are found sunk deep in the sand.
There are but few genera that can vie with the Tellina in beauty, variety, or number; some are smooth and polished, some are remarkable for their beautiful radiations, and others are covered with minute striæ and undulations; occasionally the whole surface is covered with imbrications or scales.
They are produced abundantly in almost every sea and in many rivers, but the finest species are found in the pearl-fisheries of Ceylon.
The usual form of the Tellina is broad at one end and gradually tapering towards the other. It derives its name from the Greek word τελειω, to bring to a termination.
Shell of variable form, generally striated longitudinally and very compressed; equivalve, more or less inequilateral; anterior side longer and more rounded than the posterior; offers a flexuous plait or twist at the inferior margin; summits little marked; hinge similar; one or two cardinal teeth; two distant lateral teeth, with a pit at their base in each valve; ligament external.
Tellina radiata.
T. unimaculata.
T. semizonalis.