THE NAUTILUS. 

 SOME REFERENCES TO TE.E GENUS OLIVA. 



BY JOHN FORD. 



Of all the marine univalve? tbe Olives are perhaps among the 

 most difficult to define specifically. It is true that the most irregu- 

 lar forms can in some instances be readily determined and properly 

 placed by expert conchologists, for however greatly they may differ 

 from the accepted types, certain characters, proving a common ori- 

 gin, are always perceivable. This is especially the case with such 

 species as 0. injiata Lam., 0. mnura Lam., and 0. peruv'unia Lam. 



(Fig. 1). 



To other species, however, many shells have been assigned which 

 are apparently devoid of characters necessary to sustain the rela- 

 tionship claimed for them. In this group may be included O. ara- 

 tieosa Lam., 0. irisans Lam., 0. ispidida Linn., and 0. reticularis 

 Lam. So variable both in form and color patterns are many of the 

 shells assigned to these fourspecies.it is not at all strange that they 

 have been honored with scores of specific names. That a majority 

 of these names are synonymous there is no reason to doubt, but it 

 seems equally apparent that quite a number of the shells, the names 

 of which have been thus subordinated, are really specifically dis- 

 tinct from the types with which they are associated. 



FIG. 1. FIG. 2. FIG. 3. 



0. peruviana Lam. 0. erylhrostoma Lam. 0. porphyria Lam. 



Among these may be noted 0. ornata Marratt and O. julietta 

 Duclos. which some recent writers have determined to be varieties 

 only, the former of 0. irisans, the latter of 0. unmeosa. If there 



