No. 5 (1921) ■ MADRAS AQUARIUM 91 



these they seize their prey^crabs chiefly — and drag it to their 

 mouth which is furnished with a black horny beak not unlike that 

 of a parrot. 



Few shellfish are attractive enough to be worthy of exhibition 

 in our tanks, but one, the Sacred Chank or Conch {Turbinella pinim) 

 has such absorbing interest from the religious standpoint of the 

 Hindus that an exception has to be made in its favour. This shell 

 is common on the Madras coast and is indeed the object of a 

 special fishery. It is sawn by the tens of thousands into bangles 

 at Dacca in Bengal, and few valuable bullocks in the Tamil 

 country are without a small chank tied upon the forehead. 



The eggs are deposited in a curious capsule shaped like a 

 twisted ram's horn (Fig, 23). An account of the varied roles 

 played by the chank in Indian religion and life is contained in 

 "The Sacred Chank of India " which forms Volume VII of the 

 Madras Fisheries Bulletin. 



Crabs and their allies do not live well in the tanks, due proba- 

 bly to iron contamination in the water circulation. From time to 

 time there are present examples of some of the many handsome 

 species of swimming crabs found off Madras. Of these, Neptumis 

 SiVigninolentus, marked by three livid spots on the shell covering 

 the back (carapace), and Ncptiinus pelagieiis are the most common. 

 The sexes of the latter are distinguished by great colour diver- 

 gence ; the male is a big handsome fellow with his legs brightly 

 tinted sky-blue ; the female shows a network of greyish white lines 

 on a ground of dull olive. A curious parasite called Sacculiiia, 

 allied to the ship-barnacles and acorn-shells, often attacks these 

 crabs, attaching itself under the little tail that is tucked away 

 beneath the body proper. When this happens to a male, his gay 

 blue tints fade and he assumes eventually the dull uninteresting 

 colour scheme of the female. The parasite runs a mass of rootlike 

 tubules throughout the body of its host and through these drains 

 its life blood and arrests further growth. 



Another common Madras crab is the little Dorippe dorsipes, 

 particularly interesting because it exhibits wonderful sagacity in 

 utilizing the defensive weapons of another animal for its own 

 protection. When caught in nets this little crab is usually found 

 to be using the last two pairs of its walking legs to hold in posi- 

 tion on or rather over its back, a single valve of some small clam 

 on which is seated a pale-coloured anemone. Now, all anemones 



