SYNDOSMYA. 137 
thought the Scrobicularia piperata should be amalgamated 
with the Syndosmye, 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 lamme, 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”? bemg imbedded for a foot or more 
in the pure muddy deposits of the estuaries, whilst the 
Syndosmye 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 branchie, 
and a single large palpum, broad at the base, triangular, not 
sharp-pointed nor very long, and slightly pectimated, 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, pl. 17. f. 15. 
Animal compressed, white; mantle open throughout the 
ventral range, finely frmged, forming a siphonal apparatus of 
two long, slender, separated tubes, nearly of the same length ; 
both have 5-7 short cirrhal poimts 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tubes, when not withdrawn, are corrugated, and covered with 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 laminze, of equal size, well pecti- 
nated, and also a pair—not a single palpum, as in SV. alba, if 
we are not in error with respect to that species,—of thin, short, 
broad, triangular pointed palpi, smooth without and striated 
