176 



COOKE : ON THE GENUS CUMA. 



Purpu7-a 

 Shell oblong oval, last whorl 

 large, Spire short. 



Aperture ovate, large, with 

 an oblique channel or groove 

 at the fore part. 



Columella flattened. 



Cuma 



Shell pyriform, Spire eleva- 

 ted, acute, whorls angular or 

 spinose. 



Aperture oval oblong. 



Columella convex, sometimes 

 with a strong angular tooth 

 in the middle. 



Outer Lip acute, grooved in- 

 ternally. 



Operculum ovate, blunt, nuc- 

 leus elongate, forming the 

 outer or hinder edge. 



Outer Lip simple. 



Operculum oblong, nucleus 

 elongate, forming the long 

 outer edge. 



Now, it is plain that the possession of a '■pyriform ' shell is 

 not a peculiarity of Cuma as opposed to Purpura, for Purpura 

 armigera, speciosa, and certain varieties of hcRviastoma are as 

 much ' pyriform ' as they are ' ovate-oblong ', and they have 

 never been classified as Cuma. Again an 'elevated' spireh just 

 as common in Purpura as a ' short' one, e.g. P. scobina, lapillus, 

 cingulata. And many Purpuras have 'angular' or even 'spinose' 

 whorls, e.g. P. armigera, consul, hippocastanum, echinata. 



The aperture does not present, and is not described as pre- 

 senting, any point of contrast. 



The outer lip in Purpura is described as being 'simple', in 

 Cuma as being ' acute', which I suppose is only two ways of ex- 

 pressing the same thing. It is stated however of Cuma, and is 

 not stated oi Purpura, that the outer lip is 'grooved internally'. 

 But for this to be valid as a generic distinction, it would be 

 necessary to show that no Puipurce. were internally grooved, 

 and a glance at Purp. persica, planospira, hippocastanum, and 

 hcemastoma in certain cases, will dispose of the possibility of this. 

 And, conversely, several so called Cumas are not always in- 

 ternally grooved, e.g. carinifera, gradata, and particularly kios- 



J.C, v., April, 1S87. 



