86 The Rev. R. Sheppard on two new 



4. Mytilus Macula. 



M. testa ovali, anterius compressiuscula, fragilissima, margine 



membranaceo, umbonibus decorticatis, are& antic& ad angUr 



lum adscendente. 



Tab. V. Fig. 6. 

 Habitat in stagnis. 



Long. 1 poll. 5§ lin. Lat. 2 poll. 5J lin. 



A smooth, thin, fragile shell. The hinge towards the posterior 

 extremity. Its particular character arises from the anterior area 

 being sloped upwards, so as to form an angle with the forepart 

 of the shell ; this, with the large purple blotch (which, however, 

 may be removed by rubbing with a brush), and which in some 

 specimens occupies two-thirds of the outer superficies (and 

 whence its name), stamps it as a distinct species. In the inside 

 the umbones and a small space around them are buff-colour ; the 

 rest blue, mingled however with green at the forepart of the 

 shell. 



Some specimens exceed in size the one figured ; the largest 

 [ have obtained is 1 inch 7J lines in length, by 2 inches 11 lines 

 in breadth. 



They are in vast abundance in the canals in the garden at 

 Campsey Ash, the seat of my eldest brother. 



As I have determined the characteristic of M. anatinus to be 

 the anterior slope running parallel with the base, perhaps it would 

 be as well to consider what is given as a variety of that species 

 in the Linnean Transactions to be a variety of M . Macula. 



To bring the specific differences above enumerated into one 

 point of view, Mytilus anatinus is distinguished from M.cygneus 

 by its anterior area running parallel with its base ; and again, 

 from M. Macula by the anterior area in the latter sloping up- 

 wards, 



