1898.] NATURAL SCIENCES OF PHILADELPHIA. 191 



given, it seems worth while to restate the latest and most trust- 

 worthy conclusions. 



Each tooth of Halia is shaped much like a " wish-bone," the 

 prongs forming an arched divergent base and the central projecting 

 portion at the junction, the cusp. The attached bases of the arch 

 are turned up a little and indistinctly notched on the edges ; the 

 main part of the arch is free and very prominent. When the cover 

 glass of the microscopic slide is pressed down upon the radula the 

 pillars of the arch break away from the cusp at their junction, 

 which led Poirier to regard them as a separate series of lateral 

 teeth on each side, and Fischer, not noticing Troschel's explanation 

 of this part of one of his figures, has been led into the same error in 

 regard to the analogous radula of Volutomitra. Poirier took the 

 notched bases of the broken off lateral portions of the single tooth 

 as the distal ends or cusps of his supposed laterals, directly revers- 

 ing their true position. There is only a single row of teeth. 



The position of Halia is unquestionably among the Volutacea. 

 The radula of Scaphella Tumeri as figured by Gray, is almost iden- 

 tical, and that of Volutomitra gronlandica is closely similar. Halia 

 wants the siphonal appendage of the typical Volutes and so does 

 Volutomitra. Both Scaphella and Volutomitra are without oper- 

 cula, like Halia. The external form of the foot and head is essen- 

 tially similar in all three. The texture of the shell of Halia, and 

 also its color and color-pattern, are essentially identical with those 

 of Scaphella (Aurinia) dubia Brod., which has the pillar and plaits 

 degenerate. The process of degeneration, aided by the more ample 

 whorls of Halia, has completed the effacement of the plaits and the 

 enfeeblement of the pillar or central axis of the shell. The speci- 

 men of Halia at my disposal for study is somewhat worn at the 

 apex, but the form of the nucleus indicates that, like Scaphella and 

 Volutomitra, its nepionic shell was membranous, and has left a rough 

 scar on the surface of the initial shelly coil, a view confirmed by 

 Cossmann's figure of the nucleus of a fossil species. In Aurinia 

 the degenerate radula is edentulous, but the type, which began in 

 the Eocene, and has retained its color pattern and general charac- 

 ters ever since, is abundant in the Pliocene, and may readily have 

 thrown off the aberrant Halia at that period from which it is 

 known to date. 



Halia was erected into a family by Kobelt, but it can hardly be 

 said to possess family characteristics, its essential features being 



