TESTACEA. 67 



present as in the Edulis. The flesh is reddish orange, that of the Eduhs 

 is yellowish. A quantity of strong black threads, like horse's hair, forms 

 the bi/ssus which secures the animal so firmly to solid substances, — as if 

 its origin belonged to stormy seas. These are arranged with some regu- 

 larity, and if they reach the sides of a glass vessel, the spots affixing their 

 extremities are seen in a perpendicular line, whereas those from the 

 Edulis are disposed more horizontally and with less regularity. 



By removing a specimen fourteen or fifteen minutes from its ele- 

 ment, the shell gapes and exposes the interior. 



This species is often overspread with corallines, and many parasite 

 productions indicative of its long existence. It is much more rare than 

 the Edulis, and it dwells in deeper water. In certain places where it is 

 sufficiently plentiful, the edible is said not to be found. I do not know 

 that it is taken for food, or whether it is considered safe. Some anato- 

 mists search for the larger specimens, as favourable for illustrating the 

 structure of the MoUusca, to which it belongs. 



Plate XII. 



Figs. 1, 2. Mytilus modiolus (Modiola modiolus) — The Horse Mussel, 

 reduced. 



Modiola barbata — The Bearded Mussel. — Plate XII., Figs. 5, 6. 



Specimens of a mussel considerably smaller than the preceding, but 

 larger than the Mijtilus edulis or common mussel, sometimes occur on 

 the coast, which are distinguished by their dull yellowish brown colour, 

 and a number of spinous processes, especially on the broader part. Seve- 

 ral authors consider this a distinct sjDecies. 



If it is so there is little uniformity among the specimens. One ex- 

 tending two mches and three quarters by nearly an inch and a half, bore 

 at least thirty on both valves ; the longest rising an inch. These spines 

 are much of the nature of thorns, springing from an enlarged long thick 

 oval root. 



