ANATINA. 141 



is divided in two parts by a strong deep oblique furrow by 

 which it is attached, and may be that in which the artery or 

 vein runs; the lower part of each plate is free, and can be 

 raised as far as the furrow ; we may say that the branchiae, 

 instead of being doubled, lay open and present in each the 

 same area in one large plate, as if they were in two. The 

 furrow gives the appearance of two branchise ; but it must not 

 be supposed that the upper portion nearest to the dorsal line 

 has been displaced or thrown back by accident ; it is securely 

 fixed thereto by its membrane, and thus forms a single open 

 plate. This branchial arrangement is confined to very few 

 families; the Anatina constitute its head-quarters; all the 

 species probably have it ; in this we have only detected one 

 short triangular palpum, but there may be two, or the rudi- 

 ment of a second; in A. norvegica, of the same branchial 

 form, there are two complete palpi. The foot is bluish- 

 white, not lanceolate, in the animal now described; but in 

 our notes, written many years ago, it was stated to be lanceo- 

 late, and it may be so : this apparent discrepancy perhaps 

 originates from the present animal having had a part of the 

 valve lacerated, thus preventing the full exsertion of the foot, 

 and giving it a blunt and rather clavate extremity. We pro- 

 pose this species as the type. 



Live and dead shells are frequently dredged in the coral 

 zone at Exmouth, the latter with rarely the ossicle ; in the 

 live ones great care must be taken not to remove it with the 

 animal. 



This species, termed Mya pubescens by the older authors, 

 was long considered the young of Pennant's and our A. de- 

 clivis, until, by a suite of specimens dredged by us many 

 years since, we demonstrated that it had true specific pre- 

 tensions. 



A. INTERMEDIA, nobis. 



A. villosiuscula, Macgillivray. 



Thracia villosiuscula, Brit. Moll. i. p. 224, pi. 17. f. 4, 7- 



Having examined numerous live specimens of this species, 

 it would be a mere repetition of the notes of the type to say 



