
yao 
448 
[FDIS ALB. 
NOTE ON LASAA SCALARIS, Phillipi. 
[From ‘Transactions of the Royal Society of South Australia,” 
vol. xexvii., 1913.] 
When Dr. Torr was gathering chitons at Port Arthur, in 
Tasmania, in 1912, he collected from the rocks at low tides 
a number of Turricula teresiw, Tenison-Woods, alive, which 
he kindly gave to me. Among these were six examples con- 
taining living L. scalaris. The ventral part of the Laswa was 
in the aperture of the Turricula, and the dorsal portion 
projected beyond its margin. tn two instances the umbos 
were turned towards the back part of ths aperture, and in four 
towards the front part, so that the position was not uniform. 
They filled from one-half to two-thirds of the opening of the 
shell. Their occurrence in this situation may be accidental. 
They might have fallen into the aperture in the bag of the 
collector, after having been gathered in the same locality; or 
they might have been drawn into the aperture unintentionally 
by the animal when disturbed in the water, or when placed in 
the bag. Their accidental presence seems rather unlikely, since 
six specimens were obtained, and the bivalve was so similarly © 
placed. Asthe Zurricula is siphonotomatous, and this usually 
indicates a carnivorous habit, the 7’. teresiw might have been 
consuming the bivalve, whose presence may be festal. Laswa 
scalaris, like other bivalves, is bored by predatory gasteropods. 
Other individuals taken at low tides, Port Arthur, show the 
resulting round holes, some in the right, others in the left 
valve, at varying distances from the umbo. I removed five 
of the six bivalves from the apertures, and examined them 
carefully under a stereoscopic microscope, but could detect 
no hole, however minute, and no spot where the sculpture of 
the shell had been defaced by any initial boring. The only 
damage, detected in one shell, was a minute piece removed 
from the ventral border of one valve, but this might have 
been an accidental injury. If the gasteropods feed on the 
bivalve they must have been disturbed directly they settled 
on their pr°y, and before they had rasped any circular area 
| in the shell sufficiently to leave any evidence of the process. 
| Is it possible the association is commensal? Lasca belongs to 
. the family Erycinid, in which are the genera Montacuta and — 
Kellia, both of which anchor themselves by a byssus, and _ 
| Lasea is intermediate between them in classification. It is 
commonly found alive, in abundance, in the crevices between 
the tubes of the coral-like annelid masses on piles of wharves 
and piers. If it attaches itself to the inside of the aperture 
of 7'. teresia, it would so block it as to prevent the extrusion of 
the gasteropod ; so it would need to anchor itself to some part 
of the body of its host, so as to be pushed out and drawn in 


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