94 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



(Fig. IV) are small, especially the left. The visceral sac is sparsely- 

 speckled, with occasional dots on the apical portion. The buccal mass 

 is short and globose, with a very strong retractor muscle at the base. 

 The salivary glands are quite separate and well developed. 



The jaw (Kig. XIII) is slightly arched, with no central projection. 



The formula of the radula (Fig. XIV) is 61 : 17 : 1 : 17 : 61, or 

 78 : 1 : 78. The central tooth is tricuspid, narrow, and elongate, the 

 first admedians also tricuspid. The cusps get gradually smaller until 

 about the 14th tooth, and they merge iuto the curved, aculeate teeth 

 of the laterals (Figs. 22, 25). The marginal teeth (Fig. marg.) are 

 very minute. 



The Genitalia (Figs. V-XII). — Commencing at the generative 

 aperture, the penis (Fig. Vrt) is a simple shaft, joined by the vas 

 deferens and retractor muscle at the posterior end, the epiphallus 

 being exceedingly short. Close adjacent and just within the vestibule 

 is the opening of the amatorial organ (Fig. VII), a much larger 

 muscular eversible tube than the penis, about 6 mm. in length. At its 

 further end is situated a short, sharp-pointed, transparent calcareous 

 dart, on the point of a conical tubercle (Fig. XI). The tube is here 

 contracted iuto a long, gradually tapering, rope-like duct (Fig. VIII) 

 about 8 mm. long. To the eye this has a twisted appearance, but 

 closer examination shows it to be a thinly sheathed cord (Fig. XII), 

 closely convoluted or puckered; it may thus possibly act as a spring 

 on the extension of the dart. This cord bifurcates more than once 

 (Fig. IX), and the ends are buried in a close, solid, cellular mass of 

 ellipsoidal form, folded and pointed at the anterior end, where it is 

 attached to the uterus by a short membrane (Fig. V), and thus kept 

 in position. In life no doubt this mass is less solid than as I 

 represent it ; hardened and contracted by the spirit, it would be 

 divided into lobes more or less separable. When the animal retires 

 within the shell, this glandular mass lies packed alongside, and almost 

 covers the basal portion of the dart-sac (Figs. VI and VII), the cord- 

 like connection being folded beneath it (Fig. V). The spermatheca 

 (Fig. VI) is small, with rather a thickened base, thin and fining to 

 a point, having an attachment to the uterus, close to that of the 

 dart-sac gland. 



Although the form of the teeth approaches those of D. striata from 

 Singapur, as described by Professor Semper (p. 54), there are not 

 ncarlj' so many in the row, 156 : 190 respectively. The jaw of 

 striata has a central projection which is absent in this Siam species. 

 The form of the darts also difiers {vide temper's tig., pi. iii, fig. 2\h). 

 It is thus a variety of striata. The genus can be divided into two 

 distinct sections by the form of the spermatheca, which is quite long 

 in Hugonis, nasuta, raregutlata, nemorensin, and Martini, moderately 

 long in Rumphii, very short in striata. In the first six species the 

 secretory glands of the amatorial organ are foliated, while in the last 

 two the}' are massed together. 



It is interesting to note that this genus is not recorded by 

 Drs. Paul & Fritz Sarasin, in their valuable and excellent work on the 

 fauna of Celebes (p. 33), as being found on the main island. On 



