512 
MR. OSLER’S OBSERVATIONS ON THE ANATOMY 
Cuvier states, for the obvious reason that it is itself the only floating shell-fish; 
and although its trunk is very unlike that of Buccinum undatum , to which he 
has compared it, its anatomy can leave no doubt of its carnivorous habits. 
Yet its aperture is entire, for the absence of anything like a respiratory tube 
forbids the extension of the columella from being considered as a beak. 
Or if the columellar extension in Ianthina should be held to destroy the value 
of the exception, the aperture of Natica glaucina is perfectly entire, and this 
molluscum is certainly carnivorous. It devours the baits set by fishermen near 
low water mark ; its faeces are slimy, and it is furnished with a considerable 
trunk, which bears a close resemblance to that of Buccinum lapillus, except in 
being less projectile, and is actually larger in proportion to the size of the 
animal. It is hut reasonable to suppose that many other mollusca, marked 
with the same external characters, possess a similar structure and similar 
habits ; and consequently, that the presence or absence of a beak is too ex- 
ceptionable to be received as a distinction between the carnivorous and the 
herbivorous classes. 
I suspect both Ianthina and Natica to be insectivorous. The latter is nearly 
a pelagic animal, and is never met with far from low water mark, except when 
thrown on shore by storms. The foot is large, composed of several lobes, and 
capable of being injected with water; and the animal is usually found, when 
under water, with the shell buried in the sand, while the injected foot rests 
like a mass of dead fish on the surface. May not this be a bait, to attract the 
prey which the animal is unable to pursue; and is it not probable that the 
extraordinary vesicular appendage of Ianthina may have a similar object? 
This view of the subject receives support from the situations in which the 
animals are found. Floating helplessly on every part of the ocean, it would 
appear that Ianthina can obtain no food but the insects decoyed within its 
reach. The sandy bottoms, which are the haunt of Natica, afford no marine 
plants ; it would rarely obtain carrion ; and its tongue, closely studded with 
rounded tubercles, appears not at all calculated to penetrate shells. 
To determine with exactness the anatomy of the organs of feeding in these 
animals, as well as of boring-trunks analogous to that of Buccinum lapillus ; 
the nature and action of the digestive organs in the Bulla tribe ; and the mode 
