128 MYTILID^E. 



Anglesea, in the line of strong currents, enveloped in 

 similar nests. Dr. Gray has observed that " it creeps 

 with the foot on the surface of the water, with the shell 

 downwards like a Cyclas, and it has the power, like that 

 genus, of crawling up the smooth surface of glass or 

 china." The old northern writers called it " anatum 

 cibus," its littoral habitat rendering it a tempting prey 

 to wild- fowl. According to Fabricius it is eaten, al- 

 though seldom, by the Greenlanders. 



The meaning of the specific name has reference to 

 the opposite direction in which the two sets of ribs or 

 striae appear to diverge. It is to be regretted that this 

 discordance has extended to the synonymy. Montagu 

 called the present species Mytilus discrepans ; and more 

 than ten years afterwards Lamarck used the same name 

 for Modiolaria marmorata, as well as for M. impacta, 

 a tropical shell. 



HT g * 



4. M. NI'GRA*, Gray. 



Modiola nigra, Gray, Supp. to App. to Parry's First Voyage to the North 

 Pole, p. ccxliv. Crenella nigra, F. & II. ii. p. 202, pi. xliv. f. 5, and 

 (animal) pi. Q. f. 7. 



BODY " of a transparent white hue, with the margin of the 

 cloak and siphon tinged with pink, and speckled with brown 

 and opaque white." (Alder.) 



SHELL oval, inclining to oblong, compressed, rather thin, 

 moderately glossy and slightly iridescent: sculpture, about a 

 dozen remote ribs on the anterior side, and 50-60 close-set 

 and thread-like ribs on the other side, which latter become 

 finer towards the middle of the shell; ventral area not de- 

 pressed, but without ribs ; transverse striae numerous, coarse, 

 and flexuous, sometimes forming tubercles or a rough net- 

 work where they intersect the longitudinal ribs : colour 

 purplish-brown : epidermis rather thick, fawn-colour in the 

 young, olive-green at a subsequent stage of growth, and dark 



* Black. 



