MALLEACEA, 



MALLEACEA. 



838 



The species ore found in the seas of warm climate*, more particularly 

 those of the East Indies, though some species are found westward, as 

 at the Antilles, Cape Verd, and the Azores. The species are moored 

 to the rooks and mangrore-trees by means of their byssus, and have 

 been found at depths ranging from the surface to ton fathoms. 



P. Itoynomum is an example. It is found in the East Indian Ocean. 



From specimens in IrUh limestone. 

 triangular; branch ito narrow, very long, and united nearly throughout 

 their extent. 



Shell subcorneous, delicate, elongated, flattened, irregular, inequi- 

 lateral, subequivalve, the umboues nearly anterior, distant, and a little 

 recurred ; hinge toothless, and offering simply on each valve a project- 

 ing caloeity comprehending a pit for the insertion of the ligament ; 

 muscular impression subcentraL 



The species are found in the seas of warm climates, where the 

 species, none of which are furnished with a byssus, are found in 

 Altymia, Sponges, &c. 



V. liogulaia may be taken as an example. It is found in the East 

 Indian Ocean. 



Tvlulla li*f*lata. 



a, V.ITW eloaed ; 6, inside view of rain, .bowing the hinge and muscular 

 Imprewion. 



Crtnaltda (Lam.) Animal not known, but very probably bearing a 

 close relation to that of I'erna, Shell foliated, flattened, subequivalve, 

 inequilateral, irregular, a little gaping behind, but without any aperture 

 for a byssus ; hinge linear, marginal, marked with serial crenulations, 

 which are callous and hollowed into rounded pits for the reception of 

 the divisions of the ligament ; muscular impression subcentral. 



The species inhabit the seas of warm climates, principally those of 

 the East Indies and Australia, as far as is yet known. The species, 

 which are not numerous, are not fixed by their valves nor by a byusus, 

 but, like the Vultelia, are found in submarine bodies, such as 

 sponges, Ac. 



C. wriculoidtt is an example. It is found in the seas of America, 

 especially those of the south. 



Ptrna (Brug.). Animal compressed; mantle very much prolonged 

 backwards, and fringed at its lower border; foot very small, with a 

 byssus. Shell corneous or black, lamellar, very much flattened, sub- 

 equivalve .inequilateral, very irregular, gaping in front for the passage 

 of the byssus ; hinge straight, marginal, having on each side a row of 

 small parallel furrows, which are transverse, not intrant, and in which 

 the divisions of the ligament are inserted ; muscular impression 

 subosntnL 



Pcrna IioynomHm* 



a, Valves closed, showing the bj-ssm ; i, inside view of valrc, showing hinge 

 and muscular impression. 



The number of recent Pernce given by M. Deshayes, in his 'Tables,' 

 amounts to ten recent and four fossil (tertiary). In the last edition 

 of Lamarck, the same recent number is stated, but the fossil species 

 amount to six. Professor Phillips notes one (P. quadrata, not men- 

 tioned by Lamarck or Deshayes) in the Coralline Oolite (Malton), and 

 also in the Bath Oolite. He also notices a Perna in the Oxford Clay. 

 ('Geology of Yorkshire.') The genus is recorded in the Inferior 

 Oolite, and in the Coral Rag, by Mr. Lonsdale (Oolitic District of 

 Bath, in ' Geol, Trans.'), and by Dr. Fitton, in the Lower Qreensand 

 nnd the Blackdown Sands. 



Malleia (Lam). Animal considerably compressed; mantle prolonged 

 backwards, and fringed with very small tentacular appendages ; foot 

 very distinct, canaliculated, and furnishing a byssus; buccal appendage* 

 sphericc-triangular ; branchiic short and semicircular. Shell foliated, 

 black or corneous, subnacreous, subequivalve, inequilateral, very 

 irregular, often auriculated, and presenting a hammer or T shape ; 

 mu bones not distant; an oblique notch in front for the passage of a 

 byssus ; hinge linear, very long, toothless ; with a conical oblique pit, 

 partially external, for the reception of the ligament, which is triangular 

 and subexternal; muscular impression of considerable size and 

 subcentral. 



The species inhabit the East and West Indies (Oundaloupo and 

 Martinique) and Australasia. They are found at depths ranging from 

 the surface to seven fathoms. M. Rang speaks of the species from 

 Quadaloupe and Martinique as having occurred at great depths. The 

 species, which are not numerous, are moored by their byssus to 

 submarine rooks, tc. They are very variable, and indeed M. Deshayes 

 observes that he never saw any two individuals of a species alike. Age 

 makes a considerable change in the shape of the shells, especially in 

 the auricles. 



M. De Blainville divides the genus into three sections : 1, consisting 

 of species scarcelv auricnlated (U. rultellaltu); 2, consisting of 

 uniauriculated species (M. normalit); and 3, consisting of biauriculated 

 npecies (M. vulgarii). M. Desbayes thinks that the greater part of 

 the individuals occurring in collcctioiin under the name of M. vultel- 

 lattu may be the young of the variety of if. rutyarii with short cars, 

 and he considers M. viUfeUatiu and M. anatinui as identical. 



