Sea Shells 
of New Zealand 
Plate XI 
No. 17 
pieces of pumice, each with a round hole bored right in 
the long axis. I found these to be the work of the Barnea 
similis, dead valves of that species being picked up some- 
times in that particular spot. The bore always corresponded 
with the average size of the animal. But why the surface 
of the pumice should conform in shape and direction to 
the tunnel I could not at first determine. After examin- 
ing a number of these curious objects, it occurred to me 
that the pulverised pumice formed during the boring pro- 
cess mixed with the fluid secreted by the mantle, or shell- 
making organ, of the animal, resulting in a sort of natural 
cement, which, permeating the porous walls of the tunnel, 
formed a hard core of equal thickness surrounding the 
creature. Burrowing between tide marks and below low 
water. Common in the North Island, rare in the South. 
Narrow Neck, Auckland Harbour; Mount Maunganui. 
COCHLODESMA ANGASI (cochlea, a spoon; desma, 
a ligament; Angas, the naturalist)—Commonly known as 
the Lantern shell or Spoon hinge. A fairly large, extremely 
thin and fragile, pure white, pearly bivalve, with the lus- 
trous sheen of silk; asymmetrical in shape, and having the 
right valve much fuller than the left, which is comparatively 
flat. The anterior end of the shell is rather round, while 
the posterior end is prolonged into a curious squarish sort 
of projection, much more noticeable in west coast speci- 
mens than in those from the Bay of Plenty. The valves 
gape slightly at both ends. The interior is white, rather 
pearly, and has projecting horizontally from the hinge a 
half-round hollowed-out spoon-like process for the attach- 
ment of the resilium or cartilaginous hinge pad. Support- 
ing this process is to be seen a buttress or raised band of 
callus. The valves being literally as thin as paper, and 
about two and a-half inches long, this reinforcing callus is 
very essential. Both valves present a small fissure at the 
umbones, or rounded eminences close to the beaks. At 
first sight one might be inclined to think that the shell is 
cracked, but the fissure is present in all species and genera 
of the family to which this one belongs. Examining many 
broken shells on the beach, one is struck by the number of 
instances where the beaks remain united and intact, though 
the remaining portions of the valves are missing. The 
fissures, then, instead of being a starting point for fracture, 
actually contribute to the safety of the parts. This seem- 
ing paradox, that there is strength in weakness, I leave 
to the ingenious reader to meditate upon. 
_ The Cochlodesma Angasi is not at all common, but 
live specimens have been washed ashore in fair numbers 
114 
