OLIVA.— Plate I. 



Note. — In the mouograph wliicli will accompany the 

 remaining Plates, Mr. Marrat's intention, as will be explained 

 in the preface, is rather to produce evidence than to decide 

 upon the value of specific diftereuces. In his study of affi- 

 nities, he has been led to register and nominally to admit as 

 species many forms which will perhaps appear to readers, 

 as they do to the editor, quite undistinguishable. The 

 former, however, will easily adopt their own conclusions 

 from the materials placed before them. 



Fig. 



1,2. PORPHYRIA, 1, lAnn. — 0. tentoria, Link. — Panama; 

 Mazatlan, etc. 



3. suBANGULATA, 4, PhiUj^pi. — South Seas (Filby). 



4. TiMOREA, 3, Duclos. — Timor (?) . 

 5, 6. Jdlieta, 5, Dnclos. — Mazatlan. 



7, 8. INCRASSATA, 2, Solandcv. — 0. avgidata, Lamk. — Hab. 

 Mazatlan ; Gulf of Nicoya. 



