PILSBRT : ON DORCASIA, TRIGONEPHEUS, ETC. 28!) 



length, the vas deferens terminal upon the epiphallus, as shown in 

 the figure. The atrium and vagina are short. The uterus contained, 

 in two individuals opened, two veiy large membranous egg-capsules, 

 measuring about 10 by 5 and 7 by 5 mm. The embryos were in 

 a very early stage of development. The albumen gland is well 

 developed. The ovisperm duct is not convoluted and knotted as 

 usual, but is coiled at its entrance into the side of the albumen 

 gland. The ovotestis consists of several bundles of long caeca em- 

 bedded in the digestive gland. The spermatheca is small and oval, 

 on a very long, slender duct, which bears a long diverticulum. The 

 total length of duct and diverticulum is 45 mm. ; of the diverticulum 

 19 mm. 



The free retractor muscles (PI. XIII, Fig. 2") are united for about 

 one-fourth of their length posteriorly. The right ocular retractor first 

 branches off, then the pharyngeal retractor. 



Cor ilia Humberti agrees veiy closely, it will be seen, with 

 C. erronea (Semper, 1870) in internal structure; and the additional 

 data obtained throw no light upon the affinities of the group with 

 other Helicidse. The plain lung, primitive type of kidney, and the 

 diverticulum upon the spermatheca duct are all features foreign 

 to those Helicid groups which share other structures. The suspicion 

 I formerly entertained that Cor ilia might be related to the Macroogona 

 is negatived by the knowledge we now have of the lungs of both 

 groups ; and we do not yet know enough of the anatomy of Plectopylis, 

 Stegodera, or Tratimatophora to demonstrate any relationship between 

 them and Gorilla, though it is natural to suppose that these genera 

 stand together. The genus, so far as we now know, stands by itself ; 

 and for it alone a subfamily Corillinae must be erected. This might 

 for the present be placed next to the Camseninae (Epiphallogona). 



Thersites meridionalis (Beaziee). 



In dealing with the molluscs of the Horn Expedition, Hedley has 

 shown that the genus Thersites, as limited in the " Guide to the Study 

 of Helices," contains two very distinct generic groups : Thersites 

 proper, including chiefly species of Eastern Australia, with genitalia 

 like Chloritis ; and Xayithomelon, with a penis of highly specialized 

 structure, comprising, besides the typical North Australian forms, 

 a large series of South and West Australian species, composing the 

 group of X. bifceniata and the group Angasella, formerly referred to 

 Planispira. T. meridionalis has, as would be anticipated from the 

 shell, the anatomy of Thersites proper. 



The foot in Thersites meridionalis is blackish, finely granulose, with 

 a pair of dorsal grooves, but no genital groove. The tail is rounded 

 above. There is a right body-lobe on the thick mantle-edge, but the 

 left lobe is mei'ely vestigeal. 



The pallial organs (PI. XIII, Fig. 5) have the structure usiial 

 in Epiphallogona. The hmg is copiously black-pigmented. The 

 pulmonary vein is large, with numerous small branches. 



The venation of the cardiac side is chiefly anterior, as usual. The 

 pericardium is about 4 mm. long. 



