PILSBRY : ON D on CASTA, TBIGONEPIIRUS, ETC. 



287 



teeth is effected by suppression of the entocone first, and then 

 diminution of the ectocone, which also is finally suppressed (PI. XIV, 

 Fig. 13, a group of transitional and marginal teeth). 



The pharynx is disproportionately large, of the usual short form. 

 The salirary glands are compact, and loosely united posteriorly below 

 the oesophagus. There is an enormous crop, and a very small stomach 

 (PI. XIII, Fig. 8). 



The pallial cavity (PL XIII, Fig. 7) is short and broad. The lung 

 shows conspicuous venation on both sides of the pulmonary vein, the 

 area on the cardiac side being particularly large and well supplied 

 with veins. The pulmonary vein has numerous small, but no very 

 large branches, except that a large pericardial vein is developed, 

 bearing a large, ramose, first pericardial branch. Between this and 

 the pulmonary vein a large median branch of the vena cava descends. 



The venation is not very distinct unless viewed by transmitted light. 



The kidney is large, subtriangular or rhombic, with a large cavity. 

 There is no distinct ureter, the cavity opening by a subapical pore 

 into the lung. There is no closed secondary ureter, but merely 

 a narrow band along the intestine and overhung by it. 



The genitalia of two individuals are figured (PI. XIII, Figs. 6 and 9). 

 The penis, very slender basally, is elsewhere stout, with a subterminal 

 retractor. The vas deferens is closely bound to the penis throughout, 

 and beyond it to the vagina, which is rather short. The duct of the 

 spermatheca is inserted low, and is basally enlarged. It is not long, 

 about the length of the penis, and terminates in an oblong spermatheca. 

 In one individual (Fig. 9) the spermatheca was enormously swollen, 

 and contained a large, oval, fleshy spermatophore, weakly corrugated 

 externally. The oviduct has the usual sacculated structure. The 

 albumen gland and ovotestis were not dissected out. 



The retractor muscle of the penis inserts distally on the lung floor. 

 The retractor of the right ommatophore lies between q^ ^^^ 9 branches 

 of the genital system. The free retractor muscles were not further 

 worked out. 



The Relationships of Tbwonephrus. 



The moi-phology of the pallial organs gives at once an unmistakable 

 clue to the afiinities of this group. The rich venation of the cardiac 

 side of the lung, the reflexed pericardial vein with its dominant first 

 branch, separated from the ramifications of the pulmonary vein by 

 a large branch of the vena cava, together with the short, bulky, sack- 

 like kidney with deficient ureter, are structures eminently characteristic 

 of a group composed of the genera Helicophanta, Ampelita, Stylodonta, 

 Acavus, Panda, Pedinogyra, Car y odes, and Anoglypta. This group, 

 the several members of which were brought together by the labours 

 of Semper, Hedley, and the writer, was segregated from other Helices 

 under the name Macroogona in my " Guide to the Study of Helices," ^ 

 and later was elevated to the rank of a family under the name 



1 Manual of Conchology, vol. ix, p. xxxii. 



