X UROCOPTID^E. 



noticeable, however, that neither cusp is emarginate or bifid, 

 even on the marginal teeth. In Holospira some specializa- 

 tion has made progress, the central and lateral teeth having 

 wide mesocones and no ectocones. The ectocones appear on 

 the transitional and marginal teeth, which differ from those 

 of Eucalodium and its allies in being low and wide, with one 

 or both cusps split. Epirobia (vol. xv, pi. 50, f. 6, 7) is still 

 more specialized, but in another direction. The mesocones 

 of the central and lateral teeth are broad and rounded, and 

 the ectocones are small and basal, separated from the meso- 

 cones. The marginal teeth are like those of Holospira. Both 

 shell and teeth mimic Urocoptis, though of course no affinity 

 is indicated. 



The Urocoptince have a profoundly modified radula. The 

 transverse rows of teeth run v-shaped or en chevron. The 

 general morphology of this type of tooth has been fully de- 

 scribed in vol. xv, p. 108, pi. 60, figs. 5, 6. In more primitive 

 groups, such as Cochlodinella and Autocoptis, the central 

 tooth is not very much narrower than the laterals (vol. xv, 

 pi. 61, f. 19) ; but in the Jamaican subgenera (pi. 60, f. 3, 

 4) and those of East Cuba (pi. 61, f. 17, 18) it has been 

 independently reduced. No genus of Urocoptincz has the 

 slightest traces of ectocones on the central tooth. 



In an exceedingly interesting side line of differentiation 

 the mesocones are notched (vol. xvi, pi. 14, f. 8, Macrocer- 

 amus) or squarely truncate and finely serrate (vol. xv, pi. 

 43, f. 6-13, Anoma and Spirostemma) . In the latter two 

 genera the teeth are much more numerous and minute than 

 in any other Urocoptince. 



In Pineria viequensis (vol. xvi, pi. 1, f. 13), Brachypo- 

 della (xvi, plates 9 and 10), and in the subgenus Tetrentodon 

 (vol. xv, pi. 43, fig. 4) the four inner lateral teeth are much 

 enlarged, the rest greatly reduced and functionless or nearly 

 so. The whole radula, too, is greatly lengthened and very 

 narrow. There is good ground for the belief that this spec- 

 ialization took place independently in the three groups men- 

 tioned, all arising from parent forms having the teeth of 

 Urocoptis. In Brachypodella the specialization is most ex- 



