294 Mr. A. Adams on the Genus Alaba, 



most nearly resembles Litiopa. Dr. P. P. Carpenter, who also 

 perceived the existence of the group, named it Tuberia, indi- 

 cating its relationship with Litiopa. 



In MM. Eydoux and Souleyet's figure of Litiopa melanostoma 

 in the ' Voyage of the Bonite/ the side of the foot is represented 

 as bearing four tentacular filaments, which induced Dr. Gray, in 

 his ' Guide,^ to establish the subfamily Litiopinae in the family 

 Planaxidce. In Alaba picta, A. Ad., the animal is semipellucid 

 white, delicately reticulated with red-brown lines. The tentacles 

 are filiform, obtuse at the tips, ringed with red-brown, and 

 flecked with opake white. The right tentacle is considerably 

 longer than the left. The eyes are on flattened lobes at the 

 outer bases of the tentacles. The foot is narrow, auriculate on 

 each side in front, the auricles being linear and recurved. The 

 operculigerous lobe is furnished with four long tentacular fila- 

 ments, the anterior two of which, when the animal is crawling 

 or swimming, are extended on each side, and the posterior two, 

 a little diverging, are directed backwards. This species lives in 

 two-fathoms- water sandy mud, in which grows a profusion of 

 Zostera. It is rather common between Tatiyama and the islet 

 named Takano-Sima, on the west coast of Niphon. 



The head, when the animal is in motioo, is concealed by the 

 shell, and the eyes are visible through the transparent edge. 

 The creature spins, with great rapidity, a pellucid thread from 

 a viscous secretion emitted from a gland near the end of the 

 tail, and swims, shell downwards, at the surface of the water. 

 When fatigued, it suspends itself, apex downwards, by means 

 of the glutinous thread, which is attached to the surface of the 

 water. 



Thus we find that Alaba picta agrees in its habits with the 

 account given by Sander Rang of his genus Litiopa, from which 

 genus indeed, as Dr. P. P. Carpenter has remarked, Alaba difi*ers 

 in the " want of Achatinoid truncation of the base." 



I find the species very naturally arrange themselves into three 

 subgeneric groups : — 1. Alaba, s. str., or the Litiopoid forms; 

 2. Diala, or the Cinguloid forms; and, 3, Styliferina, or the 

 Styliferoid forms. 



Genus Alaba, H. & A. Ad. 



Testa Litiopoidea, ovato-conica seu elongata, subdiaphana; anfractibus 

 pUcatis seu varicosis, vertice submamillato. Apertura ovata, labio 

 saepe vix truncate. 



1. Alaba tet^varicosa, C. B. Ad. 

 Cingula tervaricosa, C. B. Ad. 

 Hab. West Indies. 



