i 00 COLUMBELLTD.i;. 



Fischer (tigs. 76, VV), are synonyms. Dr. Sulur :vttempts to 

 distinguish these species, hut his distinctive characters of 

 coloring and sculpture are individual only, and not varietal or 

 specilic. 



Family COLUMBELLID.E. 



Shell small, usually covered by an epidermis, ovate or oblong, 

 sometimes Strombiform, anteriorly notched or produced into a 

 short canal, which is open ; inner li[) nnteriorly tubercled, outer 

 lip incurved in the middle, and usuall}- thickened and crenulated 

 on its inner margin. Animal : head elongated ; eyes near the 

 outer bases of the tentacles ; foot anteriorly produced. Oper- 

 culum corneous ; lamellar, with the nucleus basal or near the 

 centre of the outer margin. The lingual dentition of the group 

 is peculiar and readily distinguishable from that of all other 

 Gastropods ; its features persist with but little variation of detail 

 through all the subdivisions of the famil}^ of which examples 

 have been examined, except Engina. In the section Amycla, 

 Messrs. H. and A. Adams have included species such as A. 

 corniculu7n, Olivi, which are true Nassse, and the dentition of 

 this species has been hastily assumed to be that of the whole 

 group of Amycla. Other species, placed by H. and A. Adams 

 in the group Engina, undoubtedly belong to the group Sistrum 

 in Ricinula (see Manual, ii). The lingual of a single but typical 

 species of Engina has been figured by Morch (Manual, vol. iii, 

 t. 27, f. 36); it differs greatly from the Colnmbelliform type of 

 dentition, and the genus has accordingly been classified by 

 Troschel in Photim^. The shell of Engina is distinctly Colum- 

 belloid, however, and the difference of dentition need not deter 

 us from placing it in Columbellida^ since in A[a7'ginella glabella 

 (this vol., p. 6), distinct types of dentition occur in the same 

 species. 



A number of classifications of the species of Columl)ellidiTe 

 have been proposed. H. and A. Adams have adopted several 

 groups first characterized by Swainson, and have instituted some 

 others ; they are mostly of little systematic value, being founded 

 on slight differences in the form, etc., of the shell — differences 

 which do not persist throughout all the species assigned to them 



