ADDENDA. 25T 



plate 2, fi^. 19. Tlie two others have an auricular projection as 

 in the two last, I)ut the inner luargin on the inside is furnislied 

 wilii a rill only and not a detached margin, and the outer edge is 

 not reflected: these are the T. navalis, aisd the T. nana; the 

 former of which has the accessorial ap[)enda<^es elongated and 

 spuon-shaped, as is represented in our plate 2, tig. 3; the latter 

 is distinguished by the sirong |)rojectiii^' conic tooth on tho car- 

 dinal margin, hut the accessorial appendages we have not as yet 

 detected. 



Mytilus pra3cisus, p. 24. 

 We have specimens of this shell taken from the interior of 

 stones dredged in Torhay. It is a species of Saxicava, much 

 allied to tlie S. rugosa, but is Hatter and thinner, w ith tlie valves 

 more unequal. 



Mya ovalis, {). 33. 

 We observed a specimen of this species in the cabinet of Mrs. 

 Griffiths, taken among the rocks in Torhay. 



/' 

 Sphenia Bingiiami, p. 37. 

 Minute and delicate specimens are found not unfrequently 

 among the fine sand sent us by Mr. Lyons, from Tenby. / 



LisTERA conipressa, p. 61. 

 It is probable that there may be two sjjecies of this genus, as, 

 among our specimens gathered from different liabitats, we observe 

 some which have two distinct denticles in one v.tl'.e and one in the 

 other, all tjilhoni strong and erect ; others have tiiree additional 

 denticles in one valve, and (wo in the other, all oblique and rib- 

 liko. If so, the species with three oblique denticles in one valve 



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