778 PROF. G. C. BOURNE ON THE 



muscular partition separating the visceral cavity from the complex 

 glandular mass formed by the hypobmnchial gland and gonaducts 

 (PI. XXXVI. tig. 32). The ova appear to go through their matu- 

 ration-phases in this chamber, as no ripe ova are to be seen in the 

 follicles. In Aleadia and Eutrochatella this ovarian chamber is 

 sac-shaped and on tiie right side of the body, but in Pacific and 

 Oriental species, such as Pahrohelicina idee. Orohophana ponsonbi/i, 

 and Aphanoconia gouldiana, the ovarian chamber is produced into 

 a wide tiibe which stretches transverselv across the body and 

 receives the products of the follicles of a left ovarian lobe, the latter 

 being a distinct triangular lobe, projecting from the surface of the 

 visceral mass and packed close under the left columellar muscle. 

 This lobe is possibly characteristic of Pacific and Oriental species: 

 it is absent in Ahrtdia, and scarcely represented in Eutrochatella. 

 My specimens of ZucideUa were all male, and therefore I cannot 

 say whether it occurs or not in this West Indian genus. The 

 female gonaducts of Alcadia hoUandi, which are to all intents 

 and purposes identical with those of A. palUata. are depicted in 

 PI. XXXV. fig. 25 ; and figs.;30 to 35 (Pis. XXXV. et XXXVI.) 

 represent selected sections from a series passing horizont-ally 

 through the genital complex of a female of the same species, 

 fig. 30 being the uppermost and fig. 35 the lowest of the series. 



Deahng first with the macroscopical charactei's, the following 

 organs or parts can be distinguished, and as their shape and 

 relative positions are clearly indicated in fig. 25 a detailed de- 

 scription will be supei'fluous. (1) The oviduct od. is a very narrow 

 duct leading from the ovarian chamber to (2) the dilated or V- 

 shaped portion of the oviduct, in which a descending limb (oc?.") 

 and an ascending limb {od.') can be recognized. In Alcadia 

 the ascending limb is as long and of approximately the same 

 diameter as the descending limb : in its lowest third it receives 

 the short and narrow duct of a globular receptaculum seminis. 

 (3) The oot^'pe. oot., is a long, more or less dilated glandular duct 

 running parallel with the rectum in the right hand of the roof of 

 the mantle-cavity, and opening into the latter on the right side by 

 a relatively narrow aperture on a papilla which lies in a sort of 

 shallow cloaca formed by the expanded lips of the rectal opening. 

 Into the posterior end of the ootype open : the ascending limb of 

 the V-shaped part of the oviduct ; the caecum of the ootype, a sac- 

 shaped structure of considerable relative size, which lies parallel 

 to and to the inner side of the V-shaped duct ; thii'dly, the short 

 and i-ather narrow duct of (4) the vagina, vag. The last named 

 is a slender duct ■\\-ith thin walls, opening into the mantle-ca\-ity 

 close to the apertiu-e of the hypobranchial gland. It is continued 

 posteriorly into a sac, which runs back on the outside of the 

 V-shaped duct and ends blindly (this sac has been displaced in 

 fig. 25 to show it more clearly, in its natural position it would be 

 concealed by the V-shaped duct). It may be called the vaginal 

 sac. Comparing these ducts with those of the Xeritidae, parti- 

 cularly with Paranerita (2, fig. 60), it is clear that the ootype is 



