378 THE CANADIAN NATURALIST. [Dec. 



BIVALVE CRUSTACEANS FROM THE GULF OF ST. 

 LAWREXCE, DESCRIBED BY G. S. BRADY, Esq.. 

 C.M.Z.S. 



Introduction. 



Ill tbe great class of Crustacea or soft sliell-fisb, there is a 

 group of microscopic creatures, found both in fresh and salt 

 waters, which have the peculiarity of being covered with a 

 bivalved shell, which is not unlike ihat of some bivalve moliusks. 

 These are the Ostracoda of zoologists. Some of the species may 

 be found in abundance in our fresh water pools, where they move 

 about with great rapidity, and are very voracious devourers of 

 any animal substance that may come within their reach. If a 

 quantity of them be taken up in a bottle with some of the water 

 in which they live, and examined with a magnifying glass, they 

 will be seen to extend little tufted antennoe or feelers from the 

 end of the shell, and little jointed feet from the front, with which 

 they scramble along in a curious lop-sided way, but with much 

 swiftness. If a bit of meat be placed in the water, they crowd 

 around it with iireat eafrerness. and it is amazinoj to witness the 

 rapidity with which it will disappear under their attacks. These 

 fresh-water species belong to the genus Cffpris, and several species 

 occur in different parts of this country ; but the marine species 

 are much more numerous, and may be found in all depths and in 

 all latitudes. They are also an ancient tribe ; many species being 

 found in our old limestone rocks, and they seem at all periods and 

 in all places to have been among the most efficient scavengers of 

 the waters. 



The species noticed in the following lists and descriptions are 

 all from the Gulf of St. Lawrence. They were obtained from 

 specimens of marine sand and mud in the collection of Dr. 

 Dawson, and obtained by him partly in his own dredging ex- 

 peditions, and partly from dredgings and soundings by Capt. 

 Orlebar, R.N., Mr. Whiteaves, F.G.S., of Montreal, and the 

 officers of the Geological Survey. The whole of these collections 

 were placed in the hands of Mr. G. M* Dawson, for the purpose 

 of selecting the minute microscopic shells of the order Foraminifera. 

 In picking out these, any other organic bodies were also selected, 



