.I/'c</o/»^ (>/ I'aliulestiiii.i jenkinsi. 429 



are tldimer than those of tlie ventricle, and there is a ea})aciou3 

 ertorent branchial vessel. No very satisfactory sections of 

 the auriculo-ventricuiur orilice were obtained. In tiie best, 

 however, distinct traces of modifications of a valvular nature 

 were found (PI. XV. fig. 6), comparable in general to tiie 

 condition figured by Moore (8) tor Ty phobia. At the posterior 

 a})ex of the ventricle tlie anterior and posterior aorta? are given 

 otV quite close together. The first runs lorwaid across the roof 

 of the pericardium for a good distance, and then, following 

 the oesophagus, passes into a large lacuna. Tiie posterior 

 aorta passes backwards into a similar lacuna situated between 

 the stomach and intestine. Branches of an artery were found 

 ramifying in the ovary and uniting to form a single trunk at 

 aliout the same level as the commencement of the oviduct. 

 The two run parallel for a long distance down the columellar 

 region. This genital artery appears to run into the abdo- 

 minal lacuna referred to above \_cf. distribution of the poste- 

 rior aorta in Cyclostoma elegans (Garnault, I. c.)]. 



The Excretory System. 



A single kidney is found bounded by the posterior wall of 

 the pallial cavity, the pericardium, and the body-wall ; it 

 opens into tiie first-named cavity by a short, narrow, ciliated 

 canal. Making all due allowance for contraction, there is no 

 trace of a ureter such as is found in Paludma and Valvata. 



The kidney is rather triangular in section over most of its 

 area, and its ualls are slightly folded. Its distribution aiul 

 relationsiiips are as yet uncertain, but it appears to give off 

 a posterior thin-walled prolongation which ramifies among the 

 other organs. 



The Reproductive System. 

 The animal is apparently |)arthoiiogenetic (v. supra). 

 The ovary is situated as usual in the a[>ical whorls, though it 

 does not appear to extend to the actual summit. It is closely 

 applied to the liver, and can usually be seen contrasting in 

 colour with the dark hue of the latter. It lifs on the rialitof 

 the liver in each whorl, and extends downwards and inwards 

 on the columellar (right-hand) side. It consists of a number 

 of anastomosing tubules which finally mute in the oviduct. 

 The contents of the.so tubules vary with age and condition, 

 but, save in the very smallest 3j)ecimens, one usually finds a 

 certain number of dcveloi)ing oocytes of various sizes. A 

 quantity of yolk-globules is almost always seen in one or two 

 of the largest tubules. This yolk is sometimes the onlif 

 contents ot the latter. It woukl seem that there is a special 

 localization and concentration of yolk, though it is also lound 



