RADULA OF THE RACHIGLOSSA 



221 



^^>^^^ 



group are the possession of a central tooth with from one cusp 

 (Boreofusus) to about fourteen (B 1(11161), and a single lateral more 

 or less cuspidate, the 

 outer cusp of all being 

 generally much the 

 largest. Thus in Melon- 

 gena resjoertilio (Fig. 117) 

 the central tooth is tri- 

 cuspid, the central cusp 

 being the smallest, while 

 the laterals are bicuspid ; 

 in Bhurna japonica (Fig. 



118) the central tooth is 5-cusped, the two outer cusps being much 

 the smallest. The teeth, on the whole, are sharp and hooked, 



Fig. 120. — Portion of the radula of Imhricaria 

 marmorata Swains, x 80. 







Fig. 121. — Three rows 

 of teeth from the 

 radula of Fasciolaria 

 trapezium Lam. x 

 40. 



with a broad base and formidaljle cutting edge. In the Olividae, 

 Turricula, Buccinopsis, and the Muricidae the laterals are unicuspid 

 and somewhat degraded (Fig. 119). In Mitra 

 and the Fasciolariidae they are very broad and 

 / /w .1 |V\ finely equally toothed like a comb (Figs. 120, 



' - "^^ ^ 121). The whole group is destitute of marginals. 



Several remarkable peculiarities occm\ 

 Ifarpa loses the radula altogether in the adult. 

 In the young it has lost only the laterals, and 

 consists of nothing but the central tooth. 

 Marginella has no laterals ; the central tooth 

 Fig. 122.— Six teeth is small and comb-shaped, with lilunt cusps. 



from the radula of -^ ^^ ,,,,,, , n i i 



Cymbivm diadema 1^^ v oLuta the laterals are generally lost, but 



Lam., Torres strait, in Volutomitrcc and One species of Voluta^ 



they are retained. The central tooth usually 



has three strong cusps, and is very thick and coloured a deep red 



^ V. concinna, according to Scliacko [Condi. JliftJi. i. p. 12G, PI. x.\iv. f. 5) ; the 

 lateral is large, strong, unicuspid on a broad base. 



