26 PHILWDLE. 



Shell concealed in the interior of the back above the 

 gill, oval, entirely open, without more trace of a spire than 

 a curved process at the left margin ; outer lip posteriorly 

 prolonged into a point slightly turned on itself. 



Syn. Xanthonella, Gray. 



Ex. P. luteus, Quoy and Gaimard, pi. 58, fig. 2. Shell, 

 P. luteus, fig. 2, a. 



Such is the description given of this genus by the Na- 

 turalists of the " Astrolabe," who discovered the animal on 

 the reefs at Port Dorey, New Guinea, and named it, on 

 account of its uniform pale yellow colour, Bulla lutea. M. 

 Quoy further observes, that the animal both crawls and 

 swims, and that the shell, concealed in the interior of the 

 back, above the gill, approaches more to the Dolabellas 

 than to the Bullas. The position of the eyes at once dis- 

 tinguishes this genus from the CryptophtJialmus of 

 Ehrenberg, with which it exhibits perhaps the greatest 

 affinity. 



Genus CHELlDONUitA, A. Adams. 



Head elongated, with three setigerous lobes in front, 

 not bi-lobed posteriorly, but produced into a single, lanceo- 

 late, tongue-like lobe, which is extended over the back ; 

 eyes none. Mantle prolonged posteriorly into a long- 

 bifurcate tail. Foot very large, dilated on each side, 

 reflexed and embracing the head and mantle, pointed at 

 the sides in front, rounded behind. 



Shell concealed in the thickness of the mantle, flat, 

 thin, very open, scarcely involute, without spire or colu- 

 mella; outer lip produced posteriorly into a long, curved 

 process. 



Syn. Hirundinella, Gray. 



