54 



close resemblance to Unio rcdiatus, Lam., but is more inflated and has a heavier 

 shell. It occurs in the Ottrtwa River at Duck Island ; it has also been found in 

 Leamy's Lake, near Hull, i^ the Province of Quebec. 



The variety with pink/nacre has a bright orange-brown epidermis with fine 

 rays of dark green. / 



A young specimen is miove elongated transversely, has perfect umbones which 

 phow four well developed folds, and has a rugose posterior slope .similar to 

 3Iargaritana nigosa, Barn^fesi 



The soft parts have/not been preserved ; in consequence, their arrangement 

 cannot be described.] ' 



Gencs Margaritana, Schumacher. 



The shell of this g' nus differs from that of Unio in having no lateral teeth. 

 These, however, are not always entirely wanting in 3I.margaritifera, the celebrated 

 pearl mussel of Great Britain and the North Atlantic and Pacific border regions of 

 America. From the interior continental basin it is absent ; and although com- 

 mon eastward in Quebec, it has not yet been found in this vicinity. How even a 

 mollusk may affect the destinies of a nation may be inferred from the statement 

 of Seutonius, that it was the hope of obtaining pearls from M. margaritifera which 

 led to the invasion of Britain by Julius Caesar. 



Margantana marginata, Sag, occurs sparsel}' in the Rideau and Ottawa in 

 rapid water, which, indeed, is the favourite habitat of our other species also. It is 

 small, seldom of greater length than two and a half inches, moderately thin and 

 transversely wedge shaped. In colour it ranges from a dusky green to a deep 

 brown, with indistinct dark rays. The shells found here are much inferior in 

 size and colouring to specimens of the same species received from the Mohawk 

 River, New York. 



Margantana undtdata, Say, is rare in the Rideau and is not common in the 

 Ottawa, where the least unproductive locality that I know of is above the Little 

 Chaudiere along both shores of the river. In Meech's Creek it is quite plentiful, 

 especially near the abandoned rubber factory. It i^ smaller than J/, m-jrginata, 

 proportionately more inflated, brighter in colour, often so bright as to be really 

 beautiful. The distant concentric and prominent waves on the umbones from 

 which it derives its specific name, are seldom apparent except in young shells. 

 Many old specimens are as tliick and strong anteriorly as a U. ellipsis of the same 

 size, while towards the posterior margin they are as thin and fragile as the most 

 delicate anodonta ; and thus, as well as hy having cardinal and no lateral teeth, 

 M. undulala unites in itself two of the most distinctive characters of the 

 genera between which, in the plan of creation, JIargaritana has been assigned its 

 place. 



Margaritana riigosa, Barnes, the largest we have of the genup, is abundant at 

 many points along the Rideau, but is quite rare in the Ottawa. As found in the 

 former stream it resembles the typical U. comflanatus in shape but is of a greener 

 colour, and may, morever, be easily distinguished from that shell both by the 

 wrinkles which are situated along the post lateral margin up to the hinge liga- 

 ment, and, of course, by the absence of lateral teeth. A shorter truncated form is 

 occasionally met with in the same river. 



I observed a few large and exceedingly fine specimens of this margaritana at 

 the Chats Rapids, where I found tbem in a mixul company of uniones and 

 <niodonUr, thirty three in number by actual count, wliich were living together in 

 apparent harmony in an open space between thrt rocks but little if any more than 

 41 square foot in extent. 'Fhey were green in colour, and had the characteristic 

 wrinkles prominently developed. One shell exhibited in a marked degree the 

 strange deformity that its valves did not mett in a straight line, but, an inch or 

 more f. om the posterior end, were bent sharply aside about forty degrees. I 

 have noticed a few less striking instances of similar distortion in tha same 



