PLECTOPTLIS. 103 



fold at aperture, fa inch [=5 mm.]. Basal denticle [i.e. vertical 

 parietal plate j cup-shaped." 



A discrepancy occurs between the measurements originally given 

 by Gould and those supplied by Dr. Bagg ; as the diameter indi- 

 cated by the former, however, agrees with that of the photographs, 

 allowance being made for their enlargement, Gould's measure- 

 ments must, I think, be accepted as correct. 



From figs. 47 d and , which have been copied from Dr. Bagg's 

 sketches, it appears that the parietal armature consists of a 

 strong vertical plate which is concave posteriorly ; on the posterior 



d e 



Fig. 47. Plectopylis refuga. 



side there are three short horizontal folds, the upper longest, the 

 median shortest ; a short horizontal fold at the aperture is united 

 to the flexuous ridge (see fig. 470, which shows the parietal wall) ; 

 while the palatal armature appears to consist of six folds : the 

 first three short and horizontal ; the fourth strong, vertical, 

 slightly indented about the middle ; the fifth and sixth horizontal 

 and thin (see fig. 47 d, which gives the posterior aspect of both 

 armatures). Figs. 47 a-c are reproduced from the photographs of 

 the type specimens, enlarged two diameters. 



95. Plectopylis perrierae, Gude. 



Plectopylis perrierae, Gude, Science Gossip, N. s. iv, 1898, p. 231, 

 fig, 67 (shell and armature) ; ibid., Journ. Malac. vii, 1898, p. 14, 

 fig. 10. 



Plectopylis (Chersaecia) perrierae, Gude, Science Gossip, N. s. vi, 

 1899, p. 148. 



Original description: " Shell sinistral, discoid, widely and deeply 

 umbilicated, pale corneous, very finely and regularly striated, and 

 decussated by spiral lines. Suture slightly impressed, spire 



