ON THE DART OF HELIX UNDATA Lowe. 



By GEO. C. SPENCE. 



(Read before the Society, Sept. 14th, igto). 



Early in 1910 Mr. B. R. Lucas paid a visit to Madeira and brought 

 back a number of living H. nndata. He was kind enough to dis- 

 tribute some of these and I became the possessor of a few examples 

 which I dissected. I was at once struck with the peculiar form of the 

 dart, which does not appear to have been previously figured and only- 

 very briefly described. 



■Pilsbry in the " Manual of Conchology," 2nd series, vol. ix., p. 292, 

 mentions that the darts were unfortunately missing from tlie specimens 

 he examined and refers to Morch in "Journal de Conchyliologie," 

 1865, p. 390, who writes as follows: " J'ai vu un fragment du dard, 

 qui est colossal, un pcu tordu, avec une expansion lat(^rale sur chaque 

 c6t(^." 



Dart oi Helix nndata Lowe, Cross Section through Centre of Head 



X 5. of Dart of Flelix nndata Lowe. 



As will be seen from the micro-photo, kindly taken by Mr. J. 

 Wilfrid Jackson, the rounded stem rises from an expanded base, the 

 latter having a hemispherical depression, slightly crenulate round the 

 edges, in its basal portion. The stem develops two lateral expansions, 

 forming a strongly twisted sharp-pointed lanceolate head. The expan- 

 sions bear narrow loop-like markings at right angles to the central stem. 

 The twist on the whole dart is very pronounced and viewed length- 

 wise the dart has this appearance QC- Length 6 mm. The surface 

 is vitreous in appearance and microscopically papillose. 



Mr. Lucas informs me he found two fossil darts in the deposit of 

 Canigal, which appear to belong to the same species. 



The specimen figured is now in the Manchester Museum (no. 

 E.E. 2314). 



