bednall: south austealiajst polyplacophoea. 143 



Posterior valve slightly longer than wide, the central mucro but 

 slightly projecting, posterior slope slightly convex. Interior white, 

 or showing the brown in dark specimens. Sutural laminae very small, 

 and separated by a wide straight sinus. Insertion plates very short, 

 little longer than the eaves. Anterior valve with 13, intermediate 

 valves 2-2, posterior valve 14 slits. Girdle very narrow, clothed 

 with smooth scales. Length 5*75, breadth 2 mm. 



Hah. — Troubridge Shoal, St. Vincent's Gulf, on seaweed (? Zostera). 



This minute species resembles Ischnochiton juloides in general 

 features, but has much shorter valves. The megalaesthetes are 

 conspicuous under the microscope, appearing as somewhat regularly 

 arranged white dots on the lateral areas, head valve, and posterior 

 portion of tail valve, and as short white longitudinal lines on the 

 central areas. 



5. Ischnochiton (Heterozona) cakiosus (Pilsbiy). 



Heterozona cariosa (Carpenter MS.), Pilsbry : Man. Conch., ser. I, 

 vol. xiv, p. 65, pi. xxiv, figs. 20-2. 



An oblong shell, with rounded valves, of a dirty yellowish hue, 

 sometimes spotted with brown. Finely reticulated on the summits of 

 the valves, becoming coarsely divaricately striate on the side slopes. 

 Lateral areas with several riblets, which are broken up into coarse 

 uneven granules, and occasionally bifurcate. Anterior valve closely 

 radiate ; posterior valve concentrically pustulose. Girdle in the vicinity 

 of the valves crowded with large flattened projecting scales, unequal 

 in size, the marginal ones being very much smaller. The carious 

 state of the valves of very many of the specimens of this species is a 

 noticeable feature, hence the specific name. Length 52, breadth 19 mm. 



Hah. — Encounter Bay ; and many stations in both St. Vincent's 

 and Spencer Gulfs ; also Port Fairy, Victoria, where the species attains 

 a large size. 



"Australia" is the country recorded for the .species. Although 

 plentiful under blocks of limestone at several places in St. Vincent's 

 Gulf, it is not mentioned in Mr. Angas' List of South Australian 

 Shells ; nor does it appear to have been located by any collector prior 

 to this. 



6. Ischnochiton Pilsbrti, n.sp. PI. XII, Fig. 2. 



Shell oblong, elongated, with broadly arched rounded valves, not 

 carinated. Colour, imifonn ochi'aceous yellow. Anterior valve with 

 about thirty-six closely-set, radiating, finely pustidose riblets, not 

 extending to the apex, shorter riblets occurring occasionally between 

 the others at the oviter margin, the area around the apex granulose. 

 Intermediate valves coarsely unevenly granulated on the dorsal area, 

 the granules gradually transformed into coarse, uneven, slightly 

 convergent and then divergent coiTugations on the side slopes, the 

 interspaces of the coiTugations increasing in width towaitls the 

 outer edges ; lateral areas distinctly raised, naiTow, and ornamented 



