386 MR. G. C. ROBSON ON LAND AND 



information respecting the anatomy o£ the forms under discussion. The chief 

 item of interest in these additions is the fact that dissection of the form 

 diagnosed on conchological grounds and named Hemiplecta oleata by Ancey 

 (no. 21.) has resulted in the discovery that it is not referable to Hemiplecta, 

 but appears to occupy a position near Rhjsota. 



Additions to the preceding account are given below, and figures have been 

 incorporated in the text. 



Methvenia, n. gen. 



Foot-sole undivided, a large vertically-directed caudal mucous pore. The 

 penis and epiphallus are long and narrow ; the vas deferens is also very long 

 and bears an elongate cylindrical flagellum placed at a considerable distance 

 from the epiphallus ; vagina elongate. Jaw simj)le, with a median projection. 

 Radula having the marginal toeth long, unicuspidate, almost straight, and 

 furnished with a deeply excavated base. " Shell large, globose-depressed, 

 thin, with the surface irregularly granulated above, and having the fine 

 growth-lines decussated by sinuous spiral lines below " [Ancey). 



Methvenia oleata {Ancey) [v. no. 21, antea). 



The mantle, on removing the shelly is found to be pale, with numerous 

 dark brown and white flecks, and a number of elongated dark linos extending 

 transversely across the mantle from the intestinal area. 



The foot is jrrohaUy chestnut-brown in colour. It exhibits a very narrow 

 and partly evanescent periiiodium^ and a deep, vertically placed, caudal 

 mucous pore which bears two lateral extensions which impart a cruciform 

 shape to the pore. The latter character may be due to contraction in spirit. 

 Burne (Proc. Malae. Soc. ix., 1910) has described a similar appearance of 

 the mucous pore in Rhysota Foiulloyi. The foot-sole is undivided. 



The precise interpretation of the mantle-lohes is uncertain as yet. There 

 appear to be only a right cervical lobe, which encircles the pneumostome, and 

 a subdivided left cervical lobe, a condition like that seen in Rhysota (cf. Burne, 

 loc. cit.). 



Fio-. 1. 



34 35 65 66 



Radula of Methvenia oleata (Ancey). (Reichert, 4 oc. x 6 obj.) 



T\\Q jaw (fig. 2) is simple, but remarkably thick. It bears a well-marked 

 median projection. 



