MOLLUSCA. 453 



veiled state, preserved in spirits of wine, which was com- 

 municated to him by Dr LEACH of the British Museum. 

 Its history is, therefore, necessarily imperfect. The animal 

 is rounded before, and pointed behind, and dorsally protu- 

 berant. The whole body is smooth, soft, and of a greyish- 

 white colour. The shield, which adheres on all sides, is 

 destitute of any shelly plate. It is notched near its ante- 

 rior margin, at the opening of the pulmonary cavity. The 

 foot is broad, and separated from the cloak by a slight 

 fold, which, on the right side, forms a groove, leading from 

 the base of the right tentaculum to the posterior extremity 

 of the body. It is inferred from this appearance, that the 

 sexual organs are disjoined, the female parts being seated 

 in the tail, while the male organs occupy the ordinary po- 

 sition. The only species, Limacellus lactescens, is supposed 

 to have been brought from the Antilles. 



B. Shield posterior. 



In this group, the shield is .placed nearer to the tail than 

 in the preceding, and is fortified internally with a subspiral 

 plate. It contains one genus. 



16. PA KM ACELLA. -^Posterior extremity of the shield 

 containing the shell. 



The pulmonary cavity is placed underneath the shell of 

 the shield. This arrangement occasions a corresponding 

 posterior position to the heart. Along the back, from the 

 shield to the head, are three grooves, the middle one of 

 which is double. The shield itself adheres only at the pos- 

 terior portion, the anterior part being free. The internal 

 structure is similar to the slugs. The only marked difference, 

 indeed, consists in two conical appendages of the sexual ca- 

 vity, by which there is an approach to the species of Heticix. 



The Parmacella OUvieri is the only known species, and 

 was first described, and its structure unfolded, by M. Cu- 

 VIER. It was brought from Mesopotamia by M. OLIVIER. 



