NASSA DAUTZENBERGI. 79 



which are carried over the former, and l)ecoirie granulate at the point of inter- 

 section. In ISf. Da Ktzenhergi the tubercles stand out prominently as in N.jJiopinqua, 

 the connection between them, both longitudinal and spiral, being comparatively 

 inconspicuous. The two groups do not seem to be connected by intermediate 

 varieties. In one of the latter, var. crch^sisnulpfa, the sculpture is coarser than in 

 the type. 



Probably this form has been overlooked by collectors, having been taken 

 for a variety of A\ granulata. One occasionally meets with specimens in collections, 

 as at the Sedgwick Museum, Cambridge, where the difference between the two 

 has been recognised. I noticed there an example of the species in question from 

 AValton, which had been labelled Nassa sp. It is when dealing with a number 

 of specimens, however, that its true distinction becomes apparent. 



Var. simplex, S. V. Wood, Plate V, fig. 7. 



1872. Nassa retlcosa, var simplex, S. V. Wood, Mou. Crag Moll'., 1st Suppl., p. 15, tab. iv, fig. 3. 



Dimensions. — L. 10 mm. B. 5 mm. 



Distrlhutiou. — Not known living. 



Fossil : Coralline Crag : Gedgrave. Waltonian Crag : Walton- 

 on-Naze. Butleyan : Butley. 



Bemarhs. — The specimen here figured, which was obtained at "Walton, is also 

 from the Sedgwick Museum at Cambridge. It agrees with the type form of N. 

 DauJzenhergi, except that the sculpture is more delicate. It appears to correspond 

 with the shell figured by Wood as i\'^. veticosu, var. simpJv.e [oj). cit.). Its affinities, 

 however, are with the first named species, I think, rather than with the latter. 

 The mouth is different from that of any of the ])olymorphous varieties of X. rdicosa. 



Var. minuscula, nov. Plate V, fig. 8. 



Dimensions. — L. G — 8 mm. B. 4 — 6 mm. 



Distribution. — Not known living. 



Fossil : Waltonian Crag : Walton-on-Naze, Beaumont, Little 

 Oakley. Newbournian : Sutton, Bentle3^ Butleyan : Butley. Probably else- 

 where in the Red Crag. 



Reniarlis. — I have 60 or 70 specimens from Oakley of this minute shell, all 

 about the same size, corresponding with the type form of N. Dautzenhergi, except 

 that they are much smaller, and more delicately sculptured. They appear to be 

 full grown, having the mouth perfect, and the outer lip thickened and denticulate 

 within, as in that species. They may represent a case of adult but premature 

 development, similar to those discussed by Prof. H. W. Shinier of Boston in his 

 treatise on Dwarf Faunas.^ 



' American Naturalist, vol. xlii (1908), p. 472. 



