412 MOLLUSCA. MYTILID^. Modiola. 



EXTINCT SPECIES. 



1 . M. amplus. — Depressed, triangular, acutely angled at the base ; longi- 

 tudinally striated, excepting over the posterior side ; thin— Sower. Min. Conch. 

 t. vii. — In Oolite. 



2. M. antiquorum.— Elongated, ovate, rather gibbose, smooth, straight; 

 beaks obtuse, nearly close ; hinge toothed. — Sower. Min. Conch, t. cclxxv. 

 1, 2, 3.— In Crag. 



3. M. alceformis — Obovate, with an acuminated beak, curved, depressed, 

 smooth, with teeth in the hinge. Sower. Min. Conch, t. cclxxv. f. 4.— In 

 Crap. 



4. M. pectinatus — Quadrangular, oblong, gibbose, longitudinally striated ; 

 slightly curved ; beaks produced ; front straight. — Sower. Min. Conch, t. 

 cclxxxii.— Upper Oolite. 



5. M. edentulus. — Elongated, smooth ; disk obscurely keel-shaped ; beak 

 sharp ; posterior side nearly straight ; no tooth in the hinge. — Sower. Min. 

 Conch, t. ccccxxxix. f. 1 — In Green Sand. 



6. M. lanceolatus. — Lanceolate, slightly curved, smooth ; disk keel-formed ; 

 posterior side flat ; beaks acute. — Sower. Min. Conch, t. ccccxxxix. f. 2— In 

 Green Sand. 



7. M. subltevis — Oblong, triangular, rather curved ; disk obscurely keel- 

 shaped ; front straightish ; beaks acute ; lines of growth rather prominent. 

 Sower. Min. Conch, t. ccccxxxix. f. 3— Lower Oolite. 



8. M. Braardii. — Convex, straight, pear-shaped, elongated; beaks acute, 

 terminal, (within each beak a plate is extended to the opposite edge for the 

 support of a tendon, and within that is a flat angular process) — Sower. Min. 

 Conch, t. Dxxxii. f. 2 — In Crag. 



9. M. affinis. — Obliquely oblong, carinated, smooth ; sides parallel, straight ; 

 the posterior arched in the young shell ; hinge without teeth, its anterior 

 margin reflected — Sower. Min. Conch, t. Dxxxii. f. 1.— In Crag. 



10. M. crassus. — Shell very thick, ventral edge nearly straight, beak9 

 pointed. Flem. Edin. Phil. Journ. No. XXIV. 246, tab. ix. f. 3. Gregarious. 

 In limestone slate-clay and clay ironstone in the independent coal formation in 

 Scotland. 



Gen. CIV. MODIOLA. — Shell subtrans verse, equivalve ; 

 beaks nearly terminal, hinge without teeth, and the liga- 

 ment external. 



419. M. vulgaris. — Shell smooth, or slightly wrinkled, com- 

 pressed and prominent at the extremity of the ligament ; beaks 

 tumid. 



List. Conch, t. Mlvii. f. 5. Mytilus modiolus, Linn. Syst. i. 1 158. Mont. 

 Test. Brit. 165.— On hard ground beyond low water-mark. 



Length 5 or 6 inches, breadth about one-half less ; rounded at both extre- 

 mities ; cuticle thick, yellowish-brown, sometimes with simple leaf-like fila- 

 ments. In this last state, it is the Mytilus barbatus of Montagu. In some 

 cases, it is distorted by the byssus, and is then the M. umbilicatus of Pennant- 

 — This species is eagerly sought after, as a bait for cod. 



