69 



find no sign of propping; 2 well-defined slits; inside transpar- 

 ent and glossy. The eaves under a high power are numerously 

 notched, these being too shallow to term slits. The median 

 valves vary in length, but are fully three times as wide as 

 long, i.e., the longitudinal measurement is one-third that of 

 the lateral one. 



Girdle. — Very narrow, and thickly clothed with minute, 

 irregular, flattened scales, which do not appear to imbricate. 

 Darkish blotches are noticeable opposite each suture. 



Measurements. — The shell in the dried specimen is 5^ mm. 

 by 3 mm. ; it is more than likely that a live specimen would 

 measure 6 by 3 J mm. 



Locality. — I am indebted to Dr. Torr for the specimen 

 described above, and he has loaned it to me for the purposes 

 of this paper. He had it from the collection of the late 

 Professor Ralph Tate. It is labelled in his handwriting, 

 "Tapley Shoal, living on Zostera." This shoal is about 6 miles 

 from Troubridge lighthouse, south of Yorke Peninsula, in 

 South Australia. 



Type. — The type will remain in Dr. Torr's collection, but 

 he has informed me that it will ultimately be placed in the 

 South Australian Museum. 



A second specimen, measuring just under 4 mm. by about 

 2 mm., and therefore half as wide as long, was collected by 

 myself at Marino, probably on Posidonia, on February 19, 

 1910. These are the only two specimens that up to the 

 present have come under my notice. This being a well- 

 preserved, although a diminutive one, its colouration is more 

 likely to be normal than is the case with the type. I therefore 

 append a description. 



General colour. — Serpentine green (Ridgway's Colour 

 Standards, pi. xvi.). The valves 2 to 4 have the dorsal area 

 outlined with a broad V-shaped white mark. The posterior 

 and apical portions of anterior valve are white. The sides 

 are broadly and irregularly banded with white. The girdle 

 has a broad darkish blotch at the sutures; the two opposite 

 the sutures of the anterior valve are black; there are seven 

 irregularly-spaced blotches in front of same valve. 



Shell. — The shell is more beaked than is the case with 

 the type, and there is a slight elevation of the dorsal area 

 near the beak in the first four valves. Starting at the posterior 

 margin of the beak are a few shallow, circular elevations, 

 which die away towards the middle of the anterior portion 

 of the lateral area^ These elevations are only seen in some 

 lights with a high-power lens. The whole shell is highly 

 polished and transparent. 



