Dentition of Puhnonate Mollusks. s < 



The result of my examination of the lingual membrane throws 



light on the generic position of this species. It can no longer 



be retained in Caracolus, a sub-genus of Helix, as proposed by 



von Martens, since it has the dentition of the Vitrinea of von 



Martens' arrangement. It differs, however, from Zonites, in 



having no longitudinal furrows above the margin of the foot, 



and no caudal mucus-pore. It seems to belong to no described 



genus. 



Jamil us. 



Janulus stephanophora, Desh. Madeira. Dr. Hillebrand. 

 Jaw strongly arched ; ends pointed ; cutting margin with a sharp, greatly 

 produced median projection. 



Janulus bifrons, Lowe. Madeira. Dr. Hillebrand. 



Jaw smooth, with median projection. 



Lingual membrane with 34-1-34 teeth, of which four on each side are 

 laterals, all as in ZoniUs. 



HOLOGNATHA HELICEA. 

 This section contains the genera furnished with a jaw in one 

 single piece, and quadrate marginal teeth to the lingual 

 membrane. 



A. Jaw ribless. 

 I still retain this section, though several species in various 

 genera have ribs on their jaw. 



Tebennopliorus. (See Terr. Moll., V.) 



Tebennopliorus, Costaricensis, Morch. Costa Rica. Dr. W. M. 

 Gabb. 



Jaw strongly arched, of equal width to its blunt extremities. There are 

 sub-obsolete anterior ribs about the centre of the jaw, the ends of five of 

 which denticulate the cutting margin. 



The lingual dentition is figured on Plate VIII, fig. N. There are about 

 28-1-28 teeth. The centrals have a long base of attachment, with a strong- 

 line of reinforcement running parallel to its margin at the lower edge and 

 for a short distance at the sides. The reflection is small, and bears a short, 

 stout median cusp, and small stout side cusps; all three cusps bearing short, 

 stout cutting points. The lateral teeth are like the centrals, but asymmet- 

 rical by the suppression of the inner cusp and cutting point and the inner 

 lower expansion of the base of attachment. The marginals are but a modi- 

 fication of the laterals ; the inner cutting point not becoming bifid, though 

 the outer one is so on the extreme marginals. There are hardly more than 

 twelve perfect laterals on each side. The change into marginals is very 

 gradual. 



