448 



Note on Las>ca scalaris, Piiiliipi. 



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 teresice, Tenison-Woods, alive, which 

 he kindly gave to me. Among these were six examples con- 

 taining living L. scalaris. The ventral part of the Lascea was 

 in the aperture of the Turricula, and the dorsal portion 

 projected beyond its margin. In two instances the umbos 

 were turned towards the back part of the 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. As the Turricula is siphonotomatous, and this usually 

 indicates a carnivorous habit, the T . teresice might have been 

 consuming the bivalve, whose presence may be festal. LascEa 

 scalaris, like other bivalves, is bored by predatory gasteropods. 

 Other individuals taken at low tides. Port Arthur, shov/ 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 prey, 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 i Lascea belongs to 

 the family Erycinidse, in which are the genera Montacuta and 

 Eellia, both of which anchor themselves by a byssus, and 

 Lascea 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 T. teresice, 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 



