GASTEROPODA. 



167 



lobed, the two side lobes cover the front part of the shell, 

 and the hinder lobe is thrown over the back part. 



The A. cylindrica of Ehren. is found in the Indian and 

 Red Seas. 



Acer A. Midler. (Vitrella Sw.) — Shell oval, very 

 thin, flexible, truncated, and keeled, all the 

 whorls visible, and the channel provided with 

 a deep notch parallel to the suture. Animal, 

 with the tongue having in the middle a row 

 of rather quadrate teeth, and on each side 

 about twenty-one long sharp hooks. 



Bulla akera of Mull, and B. ceylanica of 

 Brug. belong to this genus. The animals lay their eggs 

 in a single row or string. 



Scaphander. Montf. (Assula Schum.) — Shell ovate, 

 pyriform, convolute, narrowed above, ex- 

 panded below ; spire depressed ; aperture con- 

 tracted above, patulous below, not canalicu- 

 lated ; no operculum. Animal, not investing 

 the shell, bulky ; capital disk large, quadrate ; 

 lateral lobes small; foot ample, but short; 

 eyes none ; gizzard of thin calcareous plates ; 

 axis of tongue unarmed, its lateral membrane scaphander u g - 



° nanus. 



armed each with a single series of uncinated 

 teeth.* — 3 species; also fossil. 



Scaphander (Bulla) lignarius is the British species ; a 

 mollusk remarkable for the size of its gizzard, which is 

 formed of large calcareous plates, having great power to 

 grind down the food. Forbes mentions that this curious 

 apparatus was formerly made into a genus, so little was its 

 real source known. 



* Forbes's British Moll. 



M 4 



