
yew YORK SHELL CLUB NOTES No.2 December 1 Page 
A TIGER IN YOUR TANK 
George A. Hanselman 
One of the most fascinating of the many species of chitons to be 
found in the San Diego area is Placiphorella velata Dall, 1879. 
Its variouS common names give an inkling of the reason: the "jockey 
cap" chiton (because the wide girdle extends to a broad "peak" at 
the forward end), the "veiled chiton," and as will appear later its 
peculiar structure, amazing habits and versatile appetite well 
merit the term “trapper chiton." 
This is illustrated by the experience of Dave Mulliner. While 
SCUBA diving with Gordon Robilliard at a 60-foot depth along the 
kelp beds off Point Loma, Dave turned over a large rock and while 
surveying the many brittle stars, sea urchins, sulphur sponges and 
juvenile abalones which called the bottom of that particular rock 
home he noted that among the crowd there was one particular small 
abalone which didn't look quite right. To check it he slid it 
carefully off the rock, and bingo! --- a large (60mm by 50mm) 
Placiphorella velata! Dave placed the chiton in his aquarium --- 
adding a second slightly smaller one which he found a week later in 
the same location --- and began observations on their feeding habits. 
Past researchers had determined by inspection of the gut content 
that unlike the vast majority of chitons, which almost universally 
feed on algae which they rasp off rocks with their radula, the Pla- 
ciphorella were at least to some extent carnivorous and included 
sponges and hydroids in their diet. 
Dr. James McLean of the Los Angeles County Museum of Natural History, 
himself a highly skilled SCUBA diver, some years ago undertook con- 
tinuing in-place observation of Placiphorella velata living at 
depths of 20 to 40 feet in the Monterey Kelp beds. The results of 
this scrutiny he published in a paper titled "Feeding Behavior of 
the Chiton Placiphorella" (Proceedings of the Malacological Society 
of London, Vol. 35, Part 1, 1962), in which he describes the chi- 
ton's use of its wide front mantle flap as an actual capture device 
to seize small amphipods and crustaceans for food. 
The Placiphorella as a genus are unique in their possession of a 
set of tentacle-like lobes or digitations located just ahead of the 
proboscis. They also possess on their abnormally wide front girdle 
flap nerve-bearing setae and papillae, respectively on the top and 
bottom of the mantle. As a Placiphorella velata sits in its perma- 
nent position on its rock it raises its mantle flap and extends the 
tentacular structure underneath it (see illustration, p. ).. Any 
contact with these structures causes the mantle flap to clamp down, 
immediately and rapidly, so as to trap any moving object which may 
have made the contact. The forward edge of the mantle then begins 
to move the trapped object back toward the proboscis, and the ten- 
tacle-like lobes appear to assist in this process, Should no food 
be trapped, or should the trapped material be deeded Sages hore! ges 
after sampling, the mantle flap is again raised and the trap reset. 
Dr. McLean noted that the chiton uses this same feeding technique 
in the aquarium as well as in its normal habitat. He also noted 
that while very small creatures could be ingested at ipl ye 
small crab slightly less than half an inch in width migh urnis 
