118 



lIELICIDiE. 



given off from the parietal ridge, revolving over less than a quarter 

 of a wliorl. The parietal armature further consists of two strong, 

 vertical, slightly cur\ed, parallel plates ; the anterior one has a 

 short horizontal support posteriorly below, and a strong hori- 

 zontal ridge anteriorly above ; the posterior one gives ofi' on the 

 posterior side two short supports, one above and one below. A 

 short, free horizontal fold occurs below the vertical plates. 

 Fig. 57 d shows the parietal wall with its plates and the fold, 

 while fig. 57/ gives the anterior view of both parietal and palatal 

 armatures. The palatal armature consists of : first, a thin hori- 

 zontal fold near the suture ; next, four short, broad, oblique, 

 nearly parallel folds, whose lower concave sides face the aperture ; 

 finally, a short thin horizontal fold near the lower suture. A 

 little above the second fold and united to its posterior extremity 

 occurs a very short straight fold, while another short, slight 

 oblique fold is found between the posterior ends of the fifth and 



Fig. 57. — Plectopylis brach?/plecfci. 



sixth folds. (See fig. 57<?, which shows the inside of the outer 

 wall with its palatal folds.) Figs. 57 d-f are from one of the 

 type specimens from Moulmain in the Mc Andrew collection of 

 the University Museum of Zoology, Cambridge, the slieils having 

 been lent for this purpose by Dr. S. F. Harmer. It measures- 

 major diam. 22, minor IS mm. ; alt. 8 mm. 



Among the shells of the genus Plectopylis in the British Museum, 

 I found two specimens in the Theobald collection, labelled Plecto- 

 pylis claihratula, Benson, from Balcadua, Ceylon. I am not 

 aware that Mr. Benson ever published this name, but Dr. PfeifFer 

 described a species belonging to RutJwenia—a section formerly 

 believed to pertain to Plectopylis, but now known to have affinity 

 with Endodonts — from Ceylon, under that name. As no species 

 of Plectopylis has ever been found in Ceylon, it is probable that 

 there is a mistake in the locality, and it is" certain that the name 

 IS wrong. Judging from the external resemblances to Plectopylis 



