GASTEROPODA TECTIBRANCHIATA. 
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the sides of the mouth. Their branchicC are tentaculiform processes or papillse disposed along the sides, 
overlying like scales, [or held erect] . They inhabit all seas. 
The CavoUna, Brug'uifere, have the habit of Eolidia, but their branchige are disposed in rows across the back. 
The Flabellines, Cuv., still exhibit the tentacula of the preceding genera, with branchiae composed of radiating 
filaments supported on five or six pedicles on each side. They approximate the Glancus; and in general it is to be 
remarked, that all the Nudibranchiata with branchiae placed upon the sides of the back are nearly affined. 
The Tergipes, Cuv., 
Are in shape like the Eolidia, but have only two tentacula, and along each side of the back there is a row 
of cylindrical branchiae, each terminated by a little sucker, which enables them to be used as feet : hence 
the creature can walk in a reversed posture. [This singular structure of the branchiae, and their pedes- 
trious use, requires to be confirmed.] The known species are very small. 
The Busiris, Risso, is knowm by its oblong body, convex back, two filiform tentacula, and behind 
them, upon the neck, two plumose branchiae. 
The Plocobranchus, Van Hasselt, has tw-o tentacula, and tw^o labial lobes, and the whole back, 
widened at the sides, covered with numerous radiating striae, which are the branchiae. In their natural 
conditions, the widened margins of the cloak are raised, and overlap each other so as to form a covering 
to the branchiae, which are thus placed in a sort of cylindrical sheath. The only species yet known is 
from the shores of Java. 
THE THIRD ORDER OF THE GASTEROPODES. 
THE INFEROBRANCHIATA. 
These have nearly the habit and organization of Doris and Tritonia, but their branchiae, 
instead of being situated upon the back, are on the sides of the body, under the projecting 
margin of the cloak, where they form tw^o long series of leaflets. [The species are strictly 
littoral, being gasteropodous and incapable of swimming.] 
The Phyllidia, Cuv. 
Their naked, and generally coriaceous cloak, is not protected by any shell. Their mouth is a small 
proboseis, and has a tentaculum at each side ; two other tentacula protrude above from two little 
cavities of the cloak. The anus is in the hinder part of the cloak, and the orifices of generation under 
I the right side in front. The heart is about the centre of the back ; the stomach is simple, membranous ; 
j and the intestine short. There are several species in the Indian ocean. 
i The Diphyllides, Cuv. — 
t Have branchiae nearly similar to those of Phyllidia, but the cloak is more pointed behind ; the head, of 
i a semicircular figure, has a pointed tentaculum on each side, and a slight tubercle : the anus is on the 
: right side. 
[The Ancylus, Geoffroy,— a fresh-water Gasteropode, with a shell similar to that of a Patella, is placed by Rang 
I in this order. He asserts that the animal is branchiferous, while the Rev. Mr. Berkeley has asserted that it is pul- 
j monated. They live in stagnant waters and in rivulets, adhering to stones and aquatic plants.] 
I 
j THE FOURTH ORDER OF THE GASTEROPODES. 
! THE TECTIBRANCHIATA.-*' 
They have their branchiae attached along the right side, or upon the back, in the form of 
more or less divided, but not symmetrical, leaflets ; these are more or less covered by the 
j mantle, in which a small shell is generally contained. They approximate the Pectinibranchiata 
* The Monoplcurohranchiata oi DUinvUla. 
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