the West Coast of Davis' 's Strait. 337 



little larger than the measurement given by Fabricius, but in all 

 other respects agrees exactly with his very admirable description. 

 The other is a single valve, and is nearly twice the size of those 

 from which that naturalist described; it measures upwards of 

 two inches and a half in breadth. 



This species has somewhat the habit of C. echinatum, from 

 which it may be readily distinguished by the absence of the tes- 

 taceous spines of that species, and by having in their place the 

 epidermis raised into a fringe of tine close cilia ; the ribs are also 

 more numerous. 



Mya Uddevallensis, Forbes. 

 Mya Uddevallensis, Forbes, Mem. of the Geol. -Survey, vol. i. 

 p. 407. 



Shell elliptical, with the posterior end much truncated ob- 

 liquely towards the basal margin ; ventricose, thickish, dirty 

 white, calcareous, irregularly wrinkled concentrically, and co- 

 vered with a strong rugged olivaceous epidermis ; tooth of the 

 hinge squarely truncated, entire; siphonal impression rather 

 short, about one-third the length of the shell, not much arched 

 forward. Length 2 inches ; breadth 2§ inches. 



This species was first noticed by Mr. Smith of Jordanhill, in 

 his paper on " The last Changes in the Levels of Land and Sea in 

 the British Islands," Wernerian Memoirs, vol. viii., as occurring 

 fossil in the newer pliocene deposits at the mouth of the Clyde. 

 It has since been observed at Uddevalla in Sweden by Mr.Lyell ; 

 and Capt. Bayfield has also found it both fossil and alive in the 

 Gulf of St. Lawrence. 



Some of our best naturalists consider this form a mere variety 

 of Mya truncata ; I am inclined, however, to dissent from this 

 opinion, which I do with some hesitation. 



Half a dozen specimens were brought in all stages of growth, 



and in all of them the siphonal impression is much shorter than 



in Mya truncata, in which it is full half the length of the shell ; 



it is likewise not so much arched forward. The shell is also 



always much more truncated, and the posterior margin slopes 



towards the base of the shell, whereas in Mya truncata it inclines 



in the (| contrary direction; the form of the tooth also slightly 



differs. \ 

 \\ 



Saxicava pholadis, Chemnitz sp. 

 Mytilus pholadis, Chemn. Conch, vol. viii. p. 154. t. 82. f. 735. 

 Mya byssifera, O. Fabr. Fauna Groenl. p. 408. 



Two specimens occurred : one is f inch long and If inch 

 broad ; the other is much smaller, and differs in no respect from 

 Saxicava rugosa, 



Ann. $ Mag. N. Hist. Vol xviii. 2 B 



