150 



parallel with the hinge line behind ; its summit, too, is concavely and 

 sinuously grooved. The sublunular tooth, which is also elongated, 

 commences at the margin of the valve opposite the base of the lunule; it 

 ascends nearly parallel with the said margin, but separated from it by a 

 deep groove, and terminates at a point opposite to the centre of the 

 lunule. 



The left valve has three hinge teeth, but no sublunular tooth. The 

 two cardinal teeth diverge rather widely from above downwards, and the 

 lateral tooth is parallel with the hinge line behind, from which it is 

 separated only by a narrow and not very deep groove. The teeth of the 

 left valve are not so well preserved as those of the right, and it is not yet 

 known whether the anterior tooth in the left valve of the specimens 

 collected by Mr. Eichardson is lai'ger than the middle one or not, though 

 it certainly is as large, or whether the lateral tooth of the same valve is 

 transversely rugose or smooth. 



Middle Shales, Division D, north-west side of Hornby Island, four 

 small single valves. Productive Coal Measures, Division A, at the 

 entrance to Departure Bay, V. I., (one imperfect valve) and on the 

 Nanaimo River, two miles and a quarter up (two examples), also at the 

 Sucia Islands, where it is rather frequent; J. Eichardson, 1871-75. 



Although specimens from the above mentioned localities are variable 

 in shape, as already mentioned, yet they do not appear to be nearly as 

 much 80 as the Indian examples of C. plana figured by Stoliczka It 

 would seem that the larger the shells the longer they are in proportion 

 to their height, and vice versa. In some of Mr. Eichardson's specimens 

 the posterior end is so short and so broadly truncated as to give a 

 subquadrate outline to the shell, but in others the anal side is produced 

 and narrowly subtruncated or bluntly pointed at its termination. Again, 

 out of twelve examples of 0. plaim from the Sucia Islands the apices of 

 •the beaks in eight are sunk decidedlj^ below the highest level of the 

 hinge line, and this appears to be always the case in adult shells, but in 

 the four remaining, the largest of wkich is scarcely an inch long, the 

 beaks are very slightly elevated. 



Sowerby's description of Venus plana is too short to be ver}^ satisfactory, 

 but his figures of the shell are excellent. Mr. Eichardson's specimens 

 are extremely like the types of the species, much more so than are the 

 four Indian examples of C. plana represented by Stoliczka, and the 

 characters of the former have been described rather minutely, to facilitate 

 a comparison between them and two or three noniinal species of Veneridoe 



