MODIOLA. 181 



plate in Soiverbys " Genera," (used, likewise, for Reeves' " Con- 

 chologia Systematica," ) very characteristically represents the shell 

 which was kindly forwarded to us for examination by Mr. Willcox. 



M. Africanus, Chemnitz. 



Knorr, Dtlices des Yeux, pt. 6. pi. 4, f. 1. 

 Mytilus Africanus, Chemnitz, Conch. Cab. vol. viii. p. 1G0, pi. 83, f. 739, 740, 

 741. 

 „ Afer, Gmelin, Syst. Naturae, p. 3358. — Lamarck, Anim. s. Vert. (ed. 

 Desh.) vol. vii. p. 44. — Hanley, Recent Shells, vol. i. p. 248. 

 „ ungidatus, junior, Dillwyn, Recent Shells, vol. i. p. 310. — Turt. Conch. 

 Diet. p. 111. — Fleming, Brit. Anim. p. 411. 

 Movie cTAfrique, Blainville, Man. Malacol. pi. 64, f. 2. 

 Encycloped. Methodique, Vers, pi. 218, f. 1. 



Introduced by Dr. Fleming tender the name of M. ungulatus, 

 but only as a straggler, adhering to the bottom of vessels from the 

 African coast. 



MODIOLA. Lamarck. 



Shell oblong-, equivalve, inequilateral, valves smooth, or 

 sulcated concentrically, invested with an epidermis, which 

 is usually filamentose, especially in young specimens. 

 Anterior side very short, beaks rarely quite terminal. 

 Hinge margin toothless, or with only a compressed tooth- 

 like callus, and rarely corrugated ; ligament linear. Mus- 

 cular scars very unequal, pallial impression obscure. 



Animal oblong, margins of mantle in all parts simple, 

 closed only to form a short, and more or less perfect tube 

 in the anal region. Foot cylindrical, with a more or less 

 cylindrical byssal gland at its base. Branchiae elongate. 

 Labial palps triangular and pointed. 



It is very difficult to draw a line between the shells of 

 this genus and those of Mytilus, and were it not for the 

 peculiar simple character of the branchial region, the 

 mantle contrasting strongly with the fringed and pinnated 



