DENTALrUM. 291 



made to include those forms having a short, broad fissure at 

 the posterior extremity in addition to being practically smooth. 

 In Fitntiaria, Stoliczka,' the shell is also smooth, but the posterior 

 extremity is furnished with a long linear slit. Lcevidentalium, 

 Cossmann,- has a smooth surface, marked only by faint lines of 

 growth ; it has no posterior fissure, and is oval in section. In 

 Schizodentalium, G. B. Sowerby,^ there are a ni;mber of small 

 longitudinal slits in line with each other in the place usually 

 occupied by the long posterior fissure, when that is present. 

 In other words, the longitudinal slit is bridged over here and 

 there. Lohantale, Cossmann,* appears to be very different to 

 other allies of Be.ntalium in being compressed, smooth, and carrying 

 two lateral ribs in the interior of the shell. 



Now, the type of the genus Dentalmm is described by authors 

 as having a truncated posterior orifice, without a notch or slit. In 

 a revision of the British Eocene Scaphopoda, ilr. R. Bullen 

 Newton, r.Gr.S., and the present writer^ agreed with those authors 

 after examining typical specimens in the British Museum, and 

 allowed the absence of a notch to mark the difference between 

 it and Entails, Gray. The latter name being preoccupied, 

 us will be noticed in the synonymy above given, we proposed 

 a new one, Entaliopsis. Subsequently, however, we noted some 

 undoubted specimens of the type species in the British Museum 

 which were furnished with a small but well-marked notch. It 

 became apparent that iudividuals of that species may or may 

 not possess a notch. The question then arose as to whether 

 the absence of a notch was due to mutilation of tlie shell, or 

 was brought about by the repairs continually carried out by 

 the animal. In this connection the observations of Professor Dall 

 may be of service. He remarks' that "species (of Bentalium) 

 with very thin shells usually live buried in soft mud, which 

 measurably protects them, but others with heavy shells appear 

 to be more versatile ; at all events, if the small end of the 



' Cretaceous Gastropoda, Mem. Geol. Surv. India, 1868, p. 439. 



* Ann. Soc. Roy. Malac. Belg. vol. xxiii. 1888, p. 7. 

 ' I'roc. Malac. Soc. Lond. vol. i. 1894, p. 158. 



♦ Aun. Soc. Roy. Malac. Belg. vol. xxiii. 1888, p. 7. 

 ' Proc. :N[alac. Soc. Lond. vol. i. 1894, p. 63. 



'= Traus. Wagner Free lust. Sci. Pliilad. vol. iii. pt. 2, 1892, p. 43G. 



