ORDER TESTACEA. 121 
side of the shell is elongated. The animal withdraws more 
completely into its shell than the preceding one, and its valves 
shut more closely ; its habits, however, are the same. 
But a single species is well known; it inhabits the seas of 
Europe, (Tellina inequivalvis.) 
Here also we find a group of some small and singular 
genera, such as 
BYSSOMIA, Cuwv., 
Where the oblong shell, which has no marked tooth, has the 
opening for the foot at about the middle of its edge, and op- 
posite the summits. The byssomia also penetrate into stone, 
corals, &c. 
A species which is provided with a byssus abounds in the 
Arctic Ocean. (Mytilus pholadis, Miill. Zool. Dan.) 
HIATELLA, Daud., 
The shell gaping, to allow the passage of the foot, near the 
middle of its edges; but the tooth of the hinge is better 
marked than in the preceding genus. Ranges of salient spines 
are frequently observed on the hind part of the shell. ‘They 
are found in sand, zoophytes, &c. 
The North Sea produces a small species, (Solen minutus, 
Lin.) 
SOLEN, Lin., 
The shell only bivalve, oblong or elongated, but the hinge 
always furnished with salient and well marked teeth, sue the 
ligament external. In the 
SoLEN, Cue. (proper), 
The shell is cylindrically elongated, and has two or three 
teeth in each valve near the anterior extremity, where the foot 
issues. The latter is conical, and enables the animal to bury 
