RADULA OF THE MITBID^. 41 3 



pointing inwards, at its inner base is one sharp almost adherent 

 denticle, outside 4-5 very small denticles, which diminish to 

 mere points, all inclining sharply inward, but for the big denticle, 

 the appearance of the tooth is degraded; "false keel" well 

 marked and deep. 



In a more mature specimen from Society Is., the flanking 

 cusps on the rhacliidian are better marked ; in the laterals tliere 

 are only 2-3 denticles outside the big one, close together on one 

 side, further apart on the other ; the framework is sharply 

 pointed towards the rhachidian, bluntly pointed on the outside. 



3. /. ollvceformis Sowb. S. Pacific. Ehachidian witli two 

 large, sharply pointed cusps, projecting well beyond a curving 

 upper margin, flanked on each side by a single small denticle 

 standing out against the mass of the tooth, its apex not reaching 

 the curve of the upper margin, sides of the tooth continue this 

 curve, base nearly straight : laterals quite bare, save for one large 

 cusp, inclining inwards, no trace of further denticulations ; upper 

 margin straight, lower curved, framewoi'k pointed towards the 

 rhachidian ; general appearance very degraded. 



Text-fio-ure 10. 



Lateral and rliacliidian tootli of Imhricaria pitnctata Swains. 



4. I. punctata 'fiw&mti. W.Maui. /j^Aac/McZ/cm 4-cusped, flanked 

 by wrinkles, the 2 large inner cusps deeply rooted, with no 

 intervening central cusp ; the 2 side cusps larger than in mar- 

 moraia : the superposed plate from which the cusps spring is 

 extended angularly at the sides : laterals 5-6-cusped, the inside 

 2 small, then 2 lai'ge ones, then one or two much smaller, di- 

 minishing rapidly, all cusps inclining sharply iuAvards ; a rather 

 shallow but wqII marked " false keel " ; general appearance 

 degraded. 



This species is often regarded as identical with ossea Reeve,. 

 and the radula is not against this view. 



Group (6) oijiammigera Reeve. 



Ehachidian 7-8-cusped on a narrow framework : laterals multi- 

 cuspid, cusps about 11-15, one or two of exaggerated size ; frame- 

 work narrowed prow-like inside, produced below into a " false 

 keel." 



1. J/. JIammigera Reeve. Durban. Ehachidian 8-9-cusped, 

 cusps narrow and sharp, set on the margin of a very narrow frame- 

 work, the 5 interior alternately larger and shorter, externals mere 



