SYNDOSMYA. 137 



thought the Scrobicularia piperata should be amalgamated 

 with the Syndosmya, but a careful review of the two ani- 

 mals in 1849 has convinced us that there are considerable 

 organic variations, particularly in the arrangement of the 

 palpi and in the size of the branchial laminae, which in 

 Syndosmya alba are of equal dimensions, but in S. piperata 

 completely discordant ; again, the habitats of the two are very 

 different, the "piperata " being imbedded for a foot or more 

 in the pure muddy deposits of the estuaries, whilst the 

 Syndosmya live in the mud of the sea-beds of the South 

 Devon coasts, two or three miles from shore, and are taken 

 alive at Exmouth, Dawlish, and Babbacombe Bays. 



Exmouth, 3rd August, 1850. 



An examination this day of large specimens, shows that 

 there are a pair on each side of nearly equal suboval branchiae, 

 and a single large palpum, broad at the base, triangular, not 

 sharp-pointed nor very long, and slightly pectinated, divided 

 in the centre by a depressed line, probably the artery; this 

 gives the aspect of two narrow palpi. This plate is connected 

 at its angular point with its fellow on the other side. 



S. PRISMATICA, Mont, et Auct. 

 S. prismatica, Brit. Moll. i. p. 321, pi. 17. f. 15. 



Animal compressed, white; mantle open throughout the 

 ventral range, finely fringed, forming a siphonal apparatus of 

 two long, slender, separated tubes, nearly of the same length ; 

 both have 57 short cirrhal points at the orifices, which are 

 sometimes obsolete ; the anal tube is of the lesser diameter, 

 but the animal often greatly inflates it, particularly the ter- 

 minus, into a bulbous or club shape, and then instantly 

 attenuates it to a filiform state as fine as a needle. The 

 tubes, when not withdrawn, are corrugated, and covered with 

 a very thin pale brown epidermis. There are, on each side, 

 a pair of suboval branchial laminae, of equal size, well pecti- 

 nated, and also a pair not a single palpum, as in S. alba } if 

 we are not in error with respect to that species, of thin, short, 

 broad, triangular pointed palpi, smooth without and striated 



