MYTILUS. 179 



Perna striatula, Retzius, Nov. Gen. Testae, p. 21. 



Mytilus extistus, (not Born, Gmelin, Dillwyn), Lamarck, Anini. s. Vert. (ed. 

 Desh.) vol. vii. p. 39. — Brit. Marine Conch, f. 22. — Des- 

 ha yes, Encyclop. Method. Vers. (Supplement), vol. ii. 

 p, 559. — Hanley, Recent Shells, vol. i. p. 244. 



Encyclopedia Method. Vers. pi. 220, f. 2 (?), 3, 4. 



Dr. Turton has introduced this W. Indian mussel among our 

 British bivalves, on account of Mr. Bean having taken it alive 

 from some floating timber at Scarborough. That gentleman, 

 however (to vehom we are indebted for specimens), confesses, with 

 his usual frankness, that he has only obtained it under circum- 

 stances which leave no doubt upon his mind of its exotic origin. 

 Our synonymy demands a few explanatory remarks. One of the 

 results of our long and studious examination of the Linnean 

 cabinet is the confirmation of M.Deshayes' conjecture of the iden- 

 tity of the Mytilus exustus of Lamarck with the lost hidens of 

 Linnaeus. The language and drawing of Schroeter leave little 

 doubt that the striatulus of his work is the same species, but the 

 original shell so named in the "Mantissa" of Linnoeus, (p. 548. 

 — Dillw. Recent Shells, vol. i. p. 308.) stated to be grey, pellucid, 

 most delicately striated, and from the Northern Ocean, will not 

 so exactly agree as is fitting for its identification. We have re- 

 ceived from the United States of N. America examples of this 

 bivalve (whose range of variation is so extensive, that we have 

 thought it advisable, for its full recognition, to aid our references 

 by a short description), as the if. cubitus of Say, but that 

 author's language (Journ. Acad. Nat. Scien. Philadelphia, vol. 

 ii. pt. ii. p. 263.) seems, at least, equally applicable to Modiola 

 sulcata, a representation of which in Lister (pi. 365), he remarks, 

 it agrees very well with, and repudiates the figures of the La- 

 marckian exustus, in the " Encyclopedic Methodique." Our 

 recollection of the types of the M. ustulatus of Lamarck (as usual, 

 inadequately characterized), tends to the supposition that they 

 were not specifically distinct ; but we will not venture to ofier 

 any positive assertion to that eflfect. The Mytili demand a close 

 inspection of the growth-line, as indicative of the natural con- 

 tour, being all of them individually affected as to the incurva- 

 tion or gibbosity of the front ventral margin, the extent of dor- 

 sal angulation, and even the arcuation or refusion of the pos- 



