19 
Pinna.—Shell longitudinal, wedge-shaped, equivalve, gaping at the summit, pointed at 
the base, the beaks straight: hinge lateral, without teeth. Ligament marginal, 
linear, very long, almost internal. 
Plate XI. Fig. 4. P. muricata. (Idem.—Linn.) 
MALLACEA.—5 Genera. 
Ligament marginal, sublinear, either interrupted by indentations or serial teeth, or wholly simple. 
Shell subinequivalve, foliated. 
CreNnatTuLa.—Shell subequivalve, flat, lamellated, rather irregular; no particular open- 
ing or pit for the byssus: hinge lateral, linear, marginal, indented; indentations 
serial, callous, hollowed into pits, which receive the ligament. 
Plate XI. Fig. 3° C. mytiloides. 
Perna.—Shell subequivalve, flattened, rather deformed, texture lamellar: hinge linear, 
marginal; composed of furrow-like, transverse, parallel, non-entering teeth, be- 
tween which the ligament is inserted. A posterior sinus, slightly gaping, situat- 
ed at the extremity of the hinge for the passage of the byssus; sides callous. 
Plate XI. Fig. 6. P. ephippium. (Ostrea ephippium.—Linn.) 
Matievs.—Shell subequivalve, rude, deformed, mostly elongated, sublobate at the base; 
beaks small, diverging: hinge without teeth; an elongated conical pit situated 
under the beaks, traversing obliquely the facet of the ligament. Ligament partly 
external, short, inserted in the sloping facet of each valve. 
Plate XI. Fig. 7. M. albus. 
Ayicuta.—Shell inequivalve, fragile, rather smooth; base transverse, straight; the ex- 
tremities produced, the anterior caudiform or tail-like; a sinus in the left valve: 
hinge linear, unidentate; a cardinal tooth in each valve under the beaks. Facet 
of the ligament marginal, narrow, channelled, not traversed by the byssus. 
Plate XI. Fig. 8. A. crocea. 
MELEAGRINA.—Shell subequivalve, rotundate, nearly square, externally squamose; the 
inferior cardinal margin straight, not caudate anteriorly ; a sinus at the posterior 
base of the valves for the passage of the byssus; the left valve being at this place 
narrow and channelled: hinge linear, without teeth. Facet of the ligament mar- 
ginal, elongated, nearly external, dilated in the middle. 
Plate XI. Fig. 9. M. margaritiferus. (Mytilus margaritiferus—Linn.) 
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