iv INTEODUCTION TO THE MOLLUSCA. 



not raise its bed in any considerable degree for ages, yet the Meinam and Camboja rivers, 

 subject to inundations which loosen the earth of their banks, must continually alter the 

 nature of the floor. The Hoang Ho, or Yellow River, alone daily contributes forty-eight 

 millions of cubic feet of earth, which may partly contribute to the turbid appearance of its 

 waters, and cause an uneven surface, inhabited chiefly by mollusks whose progression is 

 rather a succession of jumps than a gliding motion. The gradual accumulation of alluvial 

 matter must destroy large numbers of molluscous animals that live buried or at the surface 

 of the mud, and as successive generations take their place above them, which in turn suffer 

 the same fate, vast beds of accumulated shells will be formed like those among which our 

 dredging operations were conducted, which in process of time will fill up the estuaries and 

 increase the dimensions of the continent. Many new species were procured by placing the 

 produce of the dredge in large wire sieves, washing it clean by pouring water on it, and 

 picking out the small shells with forceps : in this manner several beautiful Tripkoris, Sca- 

 laria, and Liotia were obtained. In the Sooloo Islands the water is very deep outside the 

 barrier reefs, the bottom is for the most part muddy, and the tide runs between the 

 islands at the rate of four miles and a half per hour ; the Phos roseatus, reiecosus, Blain- 

 vittii, and senticosus were abundant, the caudal extremity of the animals of all the species 

 ending in a slender filament. Terebrce, Mitrce, Pectunculi, Cardites, and Comes thalassiarcfais 

 were obtained. Crossing from Sooloo, we proceeded along the east coast of Borneo, and 

 anchored for about twelve days outside a sand-bank about a mile and a half from the 

 easternmost point of the province of Unsang. This part of the coast of Borneo is very flat, 

 the bottom within the fringing reefs is sand and broken coral : numerous species of Cyprcea, 

 Rotetta, and Oliva were obtained here ; and in the large swampy lagoons and rivulets of 

 brackish water slender Melanice, Assiminece, and Neritince were collected. Within Cape Rivers, 

 at the north-western extremity of Celebes, a belt of coral extends from the extreme outer islet to 

 the southward for about a mile and a half, where it joins the main and forms a snug harbour, 

 with about eight fathoms in the bight. As there is a rise of tide of about nine feet, many 

 parts of these reefs are left bare at low water, and abound in Mollusca. In many places the 

 dark and slug-like bodies of Parmopkori, and the crawling forms of the Stomatellidee, espe- 

 cially those named by Mr. J. E. Gray Gena, which cover a portion of their shells with the foot, 

 were soon gliding about the coral beds ■ while scarce a stone was turned without disturbing 



