Mode of Progression in the Genus Lima. 23 



Art. V. On the Mode of Progression observed in the Genus 

 Lima Brug. By H. E. Strickland, Esq., F.G.S. 



In May, 1836, I was detained at Malta to perform quaran- 

 tine ; the accustomed penance to which all must submit who 

 visit the Levant. I used to beguile this tedious imprisonment 

 with watching the amphibious occupations of the Maltese 

 fishermen, in the harbour fronting the Lazzaretto. The barren 

 island of Malta teems with a vast population, who live in the 

 greatest poverty, and can with difficulty procure subsistence. 

 Land produce failing them, they take to the sea, and devour 

 indiscriminately all that they can find, whether vertebrated, 

 crustaceous, molluscous, or radiated. Among others of these 

 frutti di mare, as they are called, the Maltese are particularly 

 fond of the Lith6domus dactylus Cuv., a shell which perfo- 

 rates the limestone rocks in the same manner as the Pholas. 

 When these shells occur in detached blocks of limestone, the 

 latter are fished up by means of a large pair of iron forceps, 

 attached to ropes. The fisherman sprinkles a few drops of 

 oil on the water, and renders its surface as smooth as glass. 

 He is then enabled, by the clearness of the water, to detect 

 every object in a depth even of six fathoms, and to raise the 

 blocks of stone to the surface by means of his grappling-irons. 

 He then breaks them to pieces, and extracts the sea-dates, as 

 these perforating Lithodomi are termed. Not content with 

 those which are obtained by this means, the Maltese will dive 

 to great depths, armed with hammers and chisels, and extract 

 the dates from the solid rock. 



While watching these operations, and examining the miscel- 

 laneous productions obtained by the fishermen, I was struck 

 by the lively motions of some specimens of a Lima, about 

 ljin. in length. On placing them in a glass of sea water, 

 I found that this bivalve possesses the power of swimming in 

 great perfection. The shell opens to a much greater width 

 than any other bivalve that I am acquainted with ; and, when 

 thus filled with water, the valves are suddenly closed by a 

 rapid contraction of the adductor muscle. The water is thus 

 ejected with violence from the front margin, and causes the 

 shell to move with considerable speed in an opposite direc- 

 tion. By repeating these contractions and expansions, the 

 animal is enabled to swim in a straight course, and to an in- 

 definite distance. So great is the force with which the valves 

 are brought together, that their collision produces a snapping 

 noise, which is distinctly audible. t 



I have not observed any other molluscous bivalve which 



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