56 



Meecli's Creek. Mr. Fletcher collected a few fiae specimens of the typical form 

 in the Ottawa near the outlet of Leam>'d Lake. It is a trapezoidal, slightly com-- 

 pressed, ho'n-coloured shell. Tee dorsal margin is nearly straight and is ex- 

 tended behind, where it forms a well marked wing. 



Anodonta Leicisii, Lea, occurred to me in the Mississippi at Almonte, where 

 it appears to be abundant. It has a much smaller wing than A. Benediclii, which 

 it resembles, is more elongated, and somewhat le.<s inflattd. The beaks in per- 

 fect specimens have sharp prominent tubercles, which are arranged m a manner 

 characteristic of the species. 



Anodonta implicata, Scuj, is a species of which only a single living spe-imen 

 has been obtained. It was foimd in a deep pool near the upper end of the old 

 Chats Canal, after a search of an hour's duration, which I was led to engage in by 

 seeing on the shore a few broken valves of an anodonta not previ risly met with. 

 It is a large, thick, olive-brov.'n, elongated, cylindrical shell, with a salmon- 

 coloured nacre. 



Anodonta Footiana, Lea, is not uncommon at the Chats. It is a thin, inflated, 

 oblong, browni.sh species, obscurely radiated, and tinged with )'ellow posteriorly. 

 A darker and less elongated form from Meech's Creek is said to be '' identical with 

 shells determined by Dr. Lea as his A. Footiana," which are now in Mr. Gray's 

 cabinet. 



Anodonta lacustris. Lea, inhabits lakes in the County of Ottawa. It is brown 

 when aged, but young shells are greenish yellow. The tubercles on the beaks are 

 arranged in close, concentric waves. Every specimen found in September, 1881, 

 in a small lake in Masham, was infested by hundreds of mites, probably of the 

 species found in U. luteolun and A. fluviatilis in the Eideau Canal. The same 

 lake, which is about thirty miles from Ottawa, contains a plant, Eriocaulon 

 septangulare, not recorded in the " Flora Ottawaensis " of Mr. Fletcher. 



A7iodonta fragilis, Lamarck, is common in Meech's Lake, near the outlet. It 

 is an elongated, thin, depressed shell of a yellowish colour, with a straight dorsal 

 margin, and pearly iridescent nacre. That the form regarded as lacustris is 

 distinct from this appears to me somewhat doubtful. 



Anodonta fluviatilis, Dillwyn, occurs in great numbers in McKay's Lake, New 

 Edinburgh, and in the Rideau Canal ; but is rare in the Ottawa, where it is found 

 only in bays in which there is little or no current. In colour it ranges from a 

 bright grass green to an olive-brown, with concentric yellow bands, and innumer- 

 able narrow, obscure rays, yometimes it attains a length of six inches, but is 

 generally about a third smaller. Its large size and brilliant colouring conspire 

 to make it the finest Anodonta we have. 



Repeated microscopic examinations of the young of this shell lead me to 

 believe that the only observations which I find published on the young of the 

 Unionidie arc not altogether correct. In his " Descriptions of the embryonic 

 forms of thirty-eight species of the Unionidie," Dr. Lea, says : " The base in 

 all the species always presented the anterior and the posterior margins equal, 

 which is not the case with any of the species when fully grown. That is, if a 

 perpendicular line be raised from the middle of the basal margin to the middle of 

 the dorsal line, the right arid the left divisions will be exactly symmetrical." Now, I 

 thought that piecisely the contrary was evident when the young of A. fluviatilis 

 were observed under a high power ; and Mr. Tyrrell and Mr. Fletcher, whose 

 attention was called to the matter, thought so too. Dr. Lea, however, to whom 

 I sent some of the young, wrote that on carefully examining them, he failed to 

 notice the asymmetrical difterence which I described. The venerable patron of 

 the Unionidie, now in his ninety-first year, kindly presented me at the same time 

 with the work previously referred to on •' Embryonic Forms," and with several 

 other of his valuable publications. Here was observation opposed to observation. 

 To ascertain whether I was right or wrong, 1 made use of the line solar microscope 

 of the College of Ottawa, which gives a magnification of two thousand diameters. 



