277 



and to Dr. Torr for the examination of two small specimens 

 from Esperance Bay, in Western Australia, which place is 

 probably about the limit of its extension westward. It is 

 rather a curious fact that all the specimens from these two 

 widely-separated localities are creamy-white and show none of 

 the variations so common in the intermediate localities. * 



Juvenile Forms. — For a long time both Mr. May and 

 I have been under the impression that a number of small, 

 broad, flattish shells of 6 mm. and under in length, with a 

 uniform, shallow, granulose sculpture and smooth dorsal areas, 

 were a distinct species ; but on the examination of a very long 

 series, I have come to the conclusion that they are the juvenile 

 form of /. lincolnensis, Ashby. The smooth dorsal area in 

 this juvenile form separating it easily from the juveniles of 

 the dominant species from Tasmania. 



Ever since February, 1910, when I collected a nice 

 series of this shell at Venus Bay, South Australia, I have 

 considered it a distinct species, but was unable with imperfect 

 instruments to define its distinguishing characteristics. Prac- 

 tically none of the characteristic variations of colour pattern 

 common to /. lineolatvs, Blainville, and 7. crispits, Reeve, 

 are met with in this species. 



ISCHNOCHITON AURATUS, U. Sp. 



General Appearance. — Shell glossy, elliptical, sub- 

 carinated, arched, side slope rounded, half as wide as long, 

 finely decussated. 



Colour. — Type xanthine-orange, para-type orange-buff, 

 Ridgway's Colour Standards (pi. iii.). 



Anterior Valve. — Slope rather steep, slightly convex, 

 evenly decussated, under x 28, with small, flat, polished 

 pustules; in the outer half of valve these pustules run 

 togther, in placesj giving an ill-defined appearance suggestive 

 of concentric arrangement or growth-lines. 



Pof^terior Valve. — Mucro well defined, central, the 

 anterior portion of valve and the part imm.ediately behind 

 the mucro minutely decussated and polished, but the mucro 

 itself and surrounding portions almost smooth and very highly 

 polished. The outer half of valve decorated with three con- 

 centric, more or less broken, coarsely pustulose ribs. 



Median Valves. — Dorsal area not beaked, posterior part 

 smooth and highly polished, this feature extending into the 

 adjoining portions of pleural and lateral areas. Pleural area 

 evenly and finely decussated, highly polished, the outer por- 

 tion decorated with three concentric ribs of same character 

 as posterior valve. 



