176 PHOLADID^E. 



times the usual size; its diameter greatly exceeds the anal 

 one. There are on each side of the body a pair of long nar- 

 row symmetrical branchiae ; these are nearly of similar size, 

 reaching fully to the anterior end, from which they taper 

 gradually posteally, and lie, not free, but fixed throughout 

 their extent to within ^ an inch of the branchial compart- 

 ment ; they are pale brown ; the branchial vessels are trans- 

 verse, large, but not crowded, and present the aspect of coarse 

 pectinations. On each side of the body there is a pair of 

 the palest bluish-white, large, subsymmetrical, fleshy, pointed 

 palpi, representing very elongated triangles ; each pair is con- 

 nected with its correspondent one by fillets above and below 

 the mouth; they are strongly obliquely striated, as well as 

 reticulated, though irregularly, on the inner surface by the 

 vessels of the circulation ; on the outer side the striae or reti- 

 culations are not apparent. The branchiae at their anteal 

 angles effect a contact with the palpi at their posteal points. 

 The outer palpum of each pair appears rather less, and more 

 laminar than its fellow. These appendages are usually con- 

 sidered to be of a tentacular nature, to conduct the aliment 

 into the mouth : they may be ; but they have also branchial 

 functions, as they are connected with each other by a very 

 visible artery that coalesces with that of one of the main 

 branchiae, and I have not a doubt that leading branchial veins 

 form a similar union with those of the regular branchiae. 

 The liver is anterior, of ample volume, granular, and yel- 

 lowish-green. 



P. PARVA, Pennant. 



P.parva, Brit. Moll. i. p. Ill, pi. 4. f. 1, 2. pi. 2. f. 2; (animal) pi. F. 

 f. 3 & 3 a. 



Animal thick, subcylindrical, less elongated than its con- 

 geners; body milk-white; mantle pale bluish-white, when 

 deprived of the fugacious light-red epidermis, which, at the 

 closure of the valves, forms a line resembling a suture of a red 

 sandy colour : this division of the body causes each side of it 

 to appear banded. The mantle is closed except an aperture 

 for the foot, and is prolonged into a long retractile sheath 



