DEGRADED AND ABNORMAL RADULA 



or orange (Fig. 122); in the subgenus Amoria it is unicuspicl, 

 in shape rather like a spear -head with broadened wings; in 



Volutolyria it is of a different 

 type, with numerous unequal den- 

 ticulations, something like the 

 laterals of Mitra or Fasciolaria. 

 Of the Mitridae, Cylindromitra 

 has lost the laterals. Among the 

 Buccinidae, Baccinopsis possesses 

 a curiously degraded radula, the 

 central tooth having no cusps, but 

 being reduced to a thin basal 

 plate, while the laterals are also 

 weakened. This degradation from 

 the type is a remarkaljle feature 

 among radulae, and appears to be 

 characteristic, sometimes of a whole 

 family, e.g. the Columbellidae (Fig. 

 -Examples of degraded forms 123, B), Sometimes of a genus, 

 of radula : A, Cantha',-us pagochcs g^nietimes again of a single species. 



Reeve, Panama (nascent end), x 40 ; o o i 



A', same radula, central and front ThuS in CantllurUS (a SubgCnUS of 



portion ; B, Columbella varia Sowh., -r, ■ \ ,i t i • +. ,^" „i ■ 



Panama X 50 Buccinuiri) the radula is typical in 



the great majority of species, but in 

 C.2)ngodus Eeeve, a large and well-grown species, it is most remark- 

 ably degraded, both in the central and lateral teeth (Fig. 123, A). 

 This circumstance is the more singular since C. iKigodus lives at 

 Panama side by side with C. ringeus and C. insignis, both of which 



Fig. 124. — Three rows of the radula of Sistrum spectrum Reeve, Tonga. 

 The laterals to the risrht are not drawn in. 



xSO. 



have perfectly typical radidae. It is probable that the nature of 

 the food has something to do with the phenomenon. Thus Sistrum 

 spectrum Eeeve was found to possess a very aberrant radula, not of 

 the common muricoid type, but with very long reed-like laterals. 

 This singularity was a standing puzzle to the present writer, 



