244 MOLLUSCA. 



on the back ; the Habellina, Cuvier, having radiating retiform branchia 1 , 

 supported by five or six pedicles on each side; the Tergipes, Cuvier, 

 having the form of the Eolidia, but with only two tentacula with a range 

 of cylindrical branchiae on both sides of the back, each terminated by a little 

 sucker or cup, which is used by the animal as feet, to walk on its back. The 

 Busiris, Resso, and the Placobranchus, Van Hasselt, complete the genera ; 

 the latter are small Mollusca, inhabiting the Indian Ocean. 



The remaining genera of this order are Laniogerus, Eolidia, Caro/ina, &c. 



ORDER III. 

 INFEROBRANCHIATA. 



THE Inferobranchiata have nearly the same form and organisation observed 

 in Doris and Tritonia; but their branchiae, instead of 

 being placed on the back, resemble two long series of 

 laminae, situated on the two sides of the body, under 

 the projecting margin of the mantle. 



PHYLLIDIA, Cuvier. 



The mantle naked, usually coriaceous, and without any shell ; the mouth, a 

 small proboscis, each side of which is furnished with a tentaculum ; two others 

 project from above two small cavities in the mantle. Several species inhabit 

 the Indian Ocean. 



DIPHYLLIDIA, Cuvier. 



The branchiae similar to those of the Phyllidiae, but the posterior part of 

 the mantle more pointed; on each side of the semicircular head a pointed 

 tentaculum and a slight tubercle. 



ORDER IV. 



TECTIBRANCHIATA. 



THE branchiae along the right side or on the back, composed of laminae 

 more or less divided, but not symmetrical ; they are more 

 or ^ ess coveret ^ by tne mantle, in which a small shell 



is generally contained. They approach the I'ectinibran- 

 I'hiata in the form of the orpins of respiration, and, like 

 them, inhabit the ocean. In the Bursatella, Blumelle, 

 the lateral crests are united in front in such a manner as 

 only to leave an oval aperture for the transmission of 

 water to the branchiae, which are also deprived of a 

 protecting mantle. 



