1880.] THE GENUS GIRASlA. 295 



Jnmal.— The left dorsal lobe (U.l. Plate XXIV. figs. 3, 4, 5) is 

 large in front, and extends from the respiratory orifice to the left 

 margin. The right dorsal lobe (r.d.l.) extends from the same part 

 to the posterior right margin. The shell-lobes are connected all 

 round the periphery of the mantle-zone, but are reduced in size, and 

 present two distinct right and left contractile lobes ; the right ex- 

 tends to and covers the apex of the shell, while the left extends 

 over the edge of the body-whorl for a distance of 0'3 to 0'5 inch, 

 leaving the posterior and the greater portion of the upper surface of 

 the shell uncovered (we have here a true approach to what is seen 

 in the subgenus Macrochlamys) . The posterior margin of the shell 

 is not sunk in a depression of the hinder part of the foot, but the 

 upper surface of the foot extends in an unbroken ridge to the mantle- 

 zone. 



Extremity of the foot truncate, with a large linear mucous gland, 

 the pedal line very distinct, as well as the lateral markings on the 

 surface of the body. 



Genital aperture at the lower and outer base of the right tentacle. 

 Animal reaches quite 4 inches in length. 



Description of Genital Organs of k. gigas. Small var., Khasi Hills 

 (Plate XXV. fig. 1). — The ovo-testis was not seen; the hermaphro- 

 dite duct (h.d.) is much convoluted at the anterior end, where it 

 divides ; the shape of the albumen-gland was also unobserved, and 

 had apparently not been preserved in the spirit. The oviduct (ov.) 

 was very closely convolute, and arranged in four sharp folds upon 

 the posterior portion of the spermatheca {sj).), to which it is ap- 

 parently held by muscular tissue. The prostate is wide, regular, and 

 ribbon-like, much and closely convolute, giving off the vas deferens 

 not far above the junction of the spermatheca with the oviduct ; this 

 is very long, extending forward between the inverted eye-tentacles, 

 forming a loop among the muscles of the buccal mass. 



The penis is bent on itself at the point where the retractor muscle 

 is given off {Pc. fig. 4); and a short, blunt, rounded portion extends 

 beyond the insertion of the A-as deferens (pd.), corresponding to the 

 flagellum in some species, or the Kalksack of Semper (the CBecum 

 calciferum vasis deferentis). 



The retractor muscle of the penis has its attachment, together with 

 the eye-tentacles, in the usual position, close below the apex of the 

 shell, near the posterior margin of the body-cavity (Plate XXIV. fig. 

 3 m). 



Detailed Anatomy of Penis of G. gigas (Plate XXVI. figs. 2, 3). 

 On the removal of the outer muscular sheath, the anterior end is of a 

 hollow cone-shape (a), which, on being cut away, presented within a 

 cup-shaped depi-ession (a'), and exposed the duct of the penis. It 

 contracts suddenly, and continues as a smooth stout tube of equal size 

 for about 0'25 inch, where it expands again (6) into a stouter portion 

 of cyhndrical form, which is 0'55 inch long, and continues, with gra- 

 dually lessening thickness, up to the part where it is turned suddenly 

 backwards, and close to where the retractor muscle is given off (c). 

 On removing the outer layer a chitinous sheath was exposed lying 



