ACEPHALA TESTACEA. 399 



tinged with the most brilliant colours. They adhere to all sorts of 



bodies(l). 



Plicatula, Lam. 



The Plicatulse, separated by Lamarck from the Spondyli, have 

 nearly the same kind of hinge but no heel, and flat, almost equal, 

 irregular, plicated and scaly valves, as in many of the Ostre3e(2). 



Malleus, Lam. 



A simple pit for the ligament as in the Ostrese, where the Mallei 

 were left by Linnaeus, on account of their having the same irregular 

 and inequivalve shell, but distinguished by a notch on the side of 

 this ligament for the passage of a byssus. 



The most known species, Ostrea malleus, L.; Chemn., VIII, 

 Ixx, 655, 656, which ranks among the number of high-priced 

 and rare shells, has the two ends of the hinge extended and 

 forming something like the head of a hummer, of which the 

 valves, elongated in a transverse direction, represent the han- 

 dle. It inhabits the Archipelago of India. 

 There are some others, possibly young ones of the same species, 

 in which the hinge is not prolonged. We must be careful not to 

 confound them with the Vul3ell3e(3). 



Vulsella, Lam. 



A little salient plate inside of the hinge of each side, from one of 

 which to the other extends the ligament, otherwise similar to that 

 of the Ostreae. By the side of this plate is a notch for the byssus, 

 as in the Mallei. The shell is elongated in a direction perpendicu- 

 lar to the hinge. 



The most known species inhabit the Indian Ocean(4). 



Perna, Brug. 

 Several parallel cavities across the hinge, opposed to each other in 



(1) Spondylus gxderopus, Chemn., VII, xliv, et seq., IX, cxv; Sp. regius. Id., 

 xlvi, 471. 



(2) Spond. plicatus,\j., Chem. VII, xlvii, 479, 482; Plicat. xgyptia, Suvign. , 

 Egyp. Coq., pi. xiv, f. 5. 



(3) Ostrea vulsella, Chemn., VIII, Ixx, 657, of which the Ostrea anatina, lb. 

 658, 659, is probably a mere accidental Variety. 



(4) My a vulsella, Chemn., VI, ii, 10, II; V. spcmgiarum. Lam., Savig., Eg., 

 Coq. pi. xiv, f. 2; V. Mans, Lam., Sav., lb., f. 3. 



