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JOURNAL, R.A.S. (CEYLON). [Vol. JX. 



We discovered there two snails living as parasites on a sea- 

 star. Until now only very few parasitic snails have been 

 found. The most famous kind is Entoconctra mirabilis, which 

 lives in a holothuria, and is an animal that in appearance is 

 only with difficulty to be distinguished from an intestinal 

 worm ; but its eggs develop fully-formed young snails with 

 shell, feet, and eyes. This is a new example to show how 

 impossible it is in many cases to understand the systematic 

 position of an animal without the knowledge of its develop- 

 ment. The snails examined by us are not so extraordinarily 

 deformed as the Entoconctra, yet they have many characteris- 

 tics. Our two snails are quite different from each other : 

 they are also living on different parts of the sea-star. The 

 one which inhabits the interior of it is about a quarter of an 

 inch long, and has a well-formed somewhat hard shell. 

 Where it dwells, the body of the sea-star is inflated 

 to a spherical cavity, and when the apex of the shell 

 touches the skin of the sea-star, a little hole is formed, 

 which through the interior of the cavity is in commu- 

 nication with the outside. The snail can hardly move, 

 and thus lives like a captive in his cell. The most remark- 

 able feature is, that the mouth of this snail, which 

 is small in other species, is extended into an enormous 

 proboscis, almost twice the length of its body. This 

 proboscis is immovably connected with the inner side of 

 the body-cavity of the sea-star, and through it the snail 

 sucks the fluid of the sea-star as its nourishment. 

 Underneath the shell the snail has a gill, and for breathing 

 it requires sea-water ; this streams through the above- 

 mentioned hole into the cell of the snail. The water for 

 breathing has constantly to be renewed, and to render 

 this possible, the following apparatus serves : At the root of 

 the long proboscis rises a bell-shaped muscular fold, which 

 rests with its inner side against the shell of the snail, with 

 the outer side against the wall of the cavity, and which is so 

 large that it covers the shell completely. We have not 



