10 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



ends into wings (Figs. 3, 4, 5, 6). To this group belong V. africana, 

 Reeve, and V. ponsonhyi, Sm., and the four species of Lyria whose 

 xadula is known, viz. deliciosa, Montr., nucleus, Lam., mitrcpformis, 

 Lam., Adelaide, queketti, Sm., off Durban, the last two from the 

 Gwatkin collection. The number of rows in this group is small : 

 africana 54, ponsonhyi 53, mitrceformis 52, queketti 41, in each case 

 + nascent. 



Group C. — Rhachidian rather small, central cusp long, sharp, 

 narrow ; side cusps much shorter, tending to draw in towards the 

 central. Two species only fall under this heading, vespertilio and 

 verconis. In vespertilio (Pace 18), the side cusps are not half the 

 length of the central, and curve inward slightly, but are posited as 

 in Group A. A specimen from the Gwatkin collection confirms 

 Pace's figure. In verconis all the cusps are further reduced in size, 

 the roots of the central cusp are planted deep in the framework, 

 and the two side cusps are placed close to the central, leaving the 

 ends of the upper margin bare (Fig. 7). 



Group D. — Rhachidian unicuspid, cusp long, narrow, sharp at 

 point, mounted on a sort of buttress which is deeply imbedded in 

 the framework, base scarcely curved (Fig. 8). 



V. papulosa alone exhibits this remarkable radula, in which the 

 side cusps, which we have seen approximating to the central 

 in Group C, are completely fused into it. The analogy with Amoria is 

 remarkable. But the shape of the framework, and the number of 

 teeth in the radula, both of which difier widely from Amoria, indicate 

 quite a difierent line of development. 



The group Amoria, Volutomirta, Halia, in which a unicuspid 

 rhachidian is mounted on a strongly arcuate but very slender base, 

 has been dealt with by Dall (3), and Pace (18). The latter is no doubt 

 right in thinking that what P. Fischer (6) and Poirier (19) supposed 

 were degraded laterals in Halia are " almost certainly the broken-off 

 ends of the highly arched base of the rhachidian tooth ". Troschel 

 and others make the same mistake, with regard to Volutomitra. The 

 rows in Amoria are twice as numerous as those of any Voluta proper, 

 those in Volutomitra are more numerous still, those in Halia do not 

 seem to be known. 



Bibliography. 



1. Cooke, A. H. Cambridge Nat. History, Vol. iii. Molluscs, p. 221, 



text-fig. 122 {Melo diadema). 



2. Dall, W. H. Reports on the Results of Dredging . . . Gulf of 



Mexico, etc., Report on the Mollusca . . . Part ii : Bull. Mus. 

 C. Z., Harv. xviii, 1889, 1-492, pi. xxiv, f. 7. {Volutom. 

 grcenlandica, V. duhia, gouldiana, stearnsii, scapha.) 



3. On the genus Halia of Risso : Proc. Ac. Philad., 1898, 



pp. 190-92. 



4. Recent work on MoUusks : Science, xii, 1900, pp. 822-825 



