290 



NOTE ON THE RADULA OF PYRAMIDULA RUPESTRIS 



(Drap.). 



By E. W. BOWELL. 



(Read before the Societj-, May T3th, 1914). 



A SPECIMEN of this radula is herewith submitted to the Society. 



The radula shown was taken from an animal found by the writer 

 on the Great Doward, in the south of Herefordshire, where the 

 species is abundant. Similar specimens have been examined from 

 several localities in the county of Kent. It seems, however, to be a 

 very different form from the one figured in Mr. Taylor's Monograph 

 (vol. iii., pp. 171, 474). The present specimen bears not the slightest 

 resemblance to P. rotundata ; it is, indeed, very different in appear- 

 ance from any other of our small Helicids. The only Helicid radula 

 which it recalls is that of Helix lapicida, and the resemblance to 

 lapicida is less complete than it first appeared to be. The compari- 

 son,^ however, was made with a young specimen of lapicida, which 

 naturally possesses fewer admedians, the lateral ones being provided 

 with a distinct ectocone, as are these of rupestris, and the externals 

 having subpectinate cones. The specimen shown under the micro- 

 scope has 204 rows, 8 admedians, and ii externals. The one 

 photographed has 173 rows, 7 admedians, and 11 externals. Both 

 were adult and contained young ; five in the former case, two in the 

 latter. In both cases there was little left of the parental tissues 

 except the radula. The embryonic radulse are similar in plan to the 

 adult organ, but the admedians, which number two or three only, 

 have more markedly blunt mesocones, not yet produced into pointed 

 cusps. On their external unci, however,' the pectinations are relar 



c 



J L _i_ ™L 



tively longer and finer. The adult specimen shows a broad central 

 mesocone, occupying the whole width of the uncus. The main conic 



1 Proc. Malac. Soc, vol. viii. (1908), p. 126. 



