MITRULARIA. 137 



The oblique undulating ribs of the original figures, reproduced 

 by me, are not of specific importance, resulting from a similarly 

 sculptured surface of attachment ; they do not exist on other 

 specimens. The species is mainly characterized by its attenu- 

 ated apex, thinness and color. 



H. TICAONICUS, Sowb. PI. 41, figs. 23, 24. 



Suborbicular, with the apex posterior and recurved, closely 

 radiately striate, whitish, under a pale fulvous hairy epidermis. 

 Length, 15 mill. 



Philippines. 

 I doubt its distinctness from H. subrufus, Sowb. 



H. RUGULOSUS, Dunker (unfigured). Samoan Is. 



H. PLANATUS, Carpenter (unfigured). Mazatlan. 



H. EFFODIENS, Carpenter (unfigured). West Indies. 



H. MINOR, Garrett (unfigured). Sandwich Islands. 



Genus MITRULARIA, Sehum., 1817. ' 



M. EQUESTRIS, Linn. PI. 41, figs. 25-32 ; PL 42, figs. 33-56 ; PI. 



43, figs. 57-67, 70. 



Nearly orbicular or irregular, rather solid, varying to papy- 

 raceous, rudely convex ; whitish, or more or less stained with 

 light yellowish ; radiately closely minutely ridged, or striated, 

 outer edge of base often closely crenulated. Basal plate con- 

 cave, platter-shaped, with puckered edge. Diam. 1-25 inches. 

 China Sea, Philippines, Indian Ocean, 



Prince's IsL, W. Africa, W. Indies, 



W. Coast of Central America, Galapagos Is. 

 I have interpreted this species in accordance with general 

 usage, the Linnean species being indeterminable. The synonomy 

 includes: ? M. Dillwynii, Gray, M. umbo, Reeve (fig. 27), M. 

 Neptunii, Dillw., var. costata, Morch, M. scutulum, Reeve (figs. 

 28, 29), M. stella, Reeve (fig. 31), M. cepacea, Brod. (fig. 30), 

 M. varia, Brod. (fig. 35), M. Layardii, Reeve (fig. 33), M. 

 Adamsi, Reeve (fig. 36) = M. depressa, Ad. and Reeve, not 

 Lamarck (fossil sp.), M. alveolata, A. Ad. (fig. 34), M. Vani- 

 korensis, Quoy (fig. 38), M. cancellata, Ad. and Reeve (fig. 37), 



