122 



HELICID^. 



not convergent as in P. magnet. A comparison of the figures will 

 indicate differences in the palatal armatures of these two species. 



The type specimen is here figured and is in my collection ; 

 it measures 19 mm. in diameter. Figs. 59 a-c are natural size, 



Fig. 59. Plectopylis lissochlamys. 



while figs. 59 d-f are magnified. Fig. 59 d shows the parietal 

 and palatal barriers from the posterior side ; fig. 59 e a part of 

 the parietal wall with its Iamina3 and fold ; and fig. 59/ the 

 inside of the outer shell-wall with its folds and denticles. 



107. Plectopylis magna, Gude. 



Plectopylis magna, Gude, Science Gossip, N. s. iv, 1897, p. 70, 

 fig. 52 (shell and armature) ; Journ. Malac. vii, 1898, p. 9, fig. 7. 

 Plectopylis (s. s.) magna, Gude, Science Gossip, N. s. vi, 1899, 

 p. 148. 



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

 deeply urabilicated, horny brown, finely and regularly ribbed. 

 Suture slightly impressed, spire depressed, apex scarcely raised. 

 Whorls 7|, a little rounded above, tumid below, increasing very 

 slowly, the last widening a little towards the aperture, descending 

 somewhat slowly in front, and a little constricted behind the 

 peristome. Aperture elliptical, peristome white, thickened and 

 reflexed, margins scarcely converging. Parietal callus with a 

 raised flexuous ridge, separated from both margins of the peristome 

 by a little notch. Umbilicus wide and deep. Parietal wall with 

 a short, entering, flexuous, horizontal fold, which terminates at a 

 distance of two millimetres from the parietal ridge at the aperture, 

 and having at one-third of the circumference from the aperture 

 two strong transverse plates ; the posterior one the longer, 

 vertical, and a little flexuous, giving off a short, obliquely raised 

 ridge posteriorly above, and a short, strong, obliquely deflected 

 ridge posteriorly below ; the anterior one oblique, the upper ex- 

 tremity converging towards the posterior plate, where it gives off 

 posteriorly a short, strong ridge, and anteriorly a strong, longer 

 ridge, which becomes attenuated ; at the lower extremity it gives 



