2. Genus Modiola. Pl. [VIII].
Animal. As above.
Separated by Lamarck from the Mytilus, on account of its being more transverse than longitudinal, the beaks instead of being terminal are placed beneath the apex.
Shell. Smooth, subtransverse, equivalve, regular, subtriangular, posterior side short; summits nearly lateral; hinge toothless, linear and lateral; ligament partly interior, situated in a marginal furrow; one sublateral, elongated muscular impression in each valve. Inhabits the British and American seas. Thirty-two species.
- Modiola Guyanensis.
- M. pulex.
- M. discors.
- M. cinnamorea.
- M. plicata.
- M. lithophaga.
- M. Adriatica.
- M. discrepans.
- M. trapezina.
- M. silicula.
- M. semen.
- M. lævigata.
- M. Papuana.
- M. tulipa.
- M. albicosta.
- M. vagina.
- M. picta.
- M. sulcata.
- M. plicatula.
- M. semifusca.
- M. purpurata.
- M. barbata.
- M. caudigera.
- M. squamosa.
- M. securis.
- · · · · ·
- M. Americana.*
- M. castanea*
- M. opifex.*
- M. capax.*
- M. recta.*
- M. Carolinensis.*
- M. semi-costata.*
3. Genus Pinna. Pl. [VIII].
Animal. Body oval, elongated, moderately thick, enveloped in a mantle closed above, open below, and especially to the rear, where it forms sometimes a sort of tube furnished with tentacular cirri: a flabelliform abdominal appendage, and a very considerable byssus; mouth provided with double lips, beside two pairs of labial appendages; a single large retractile muscle apparent.
Shell. Subcornate, fibrous, brittle, regular, equivalve, longitudinal, triangular, pointed anteriorly, in which direction is the summit, which is straight, wide, and frequently truncated posteriorly; hinge dorsal, longitudinal, linear, toothless; ligament occupying nearly all the dorsal edge of the shell; a single and very wide muscular impression posteriorly; a trace of the anterior in the summit. Inhabits the Mediterranean Sea. Fifteen species.
- Pinna rudis.
- P. seminuda.
- P. nobilis.
- P. marginata.
- P. pectinata.
- P. ingens.
- P. varicosa.
- P. flabellum.
- P. angustina.
- P. squamosa.
- P. muricata.
- P. saccata.
- P. dolabrata.
- P. vexillum.
- P. nigrina.