12 



H. Adams, as a dominant species with ruhrostratus, Torr, 

 either as a sub-species or as a synonym, being the name distin- 

 guishing the juvenile form. 



It should be mentioned that some of the forms above 

 referred to show sub-cutaneous lining and others short longi- 

 tudinal rows of shallow holes near the beak on the dorsal area. 

 The following resume may be helpful : — 



Minute, slender, girdle spicules: gahrieli, costatus, suh- 

 viridis. 



Coarse, girdle spicules : speciosus, ruhrostratus. 



Broad, pinnatifid, dorsal area in juvenile: gahrieli and 

 costatus. 



Narrow, pinnatifid, dorsal area : speciosus, ruhrostratus^ 

 suh-viridis. 



Small pustules and no ribs behind mucro: speciosus and 

 ruhrostratus. 



ACANTHOCHITON MAYI, n. Sp. 



Introduction. — A number of median valves of a rather 

 striking Acanthochiton were dredged by Mr. W. L. May in 

 various parts of Tasmania, in depths varying from 60 fms. to 

 100 fms. It is such a distinct species and the valves are so 

 well preserved that one seems well justified in describing it 

 without waiting for the discovery of the whole shell. I have 

 much pleasure in calling it after Mr. W. L. May, the dis- 

 coverer, and a gentleman who has done such splendid work in 

 conchology. 



Specimen No. 1. Type. 



Median valve. — Colour pale cream, very strongly carin- 

 ated, prominently beaked, dorsal area well defined, fairly broad 

 but sides almost parallel, i.e., after attaining half -growth the 

 sides of this area do not diverge. The central ridge and the 

 two sides of this area continue as smooth ribs the whole length 

 of the valve; the space between is cut up by short, deep, 

 longitudinal grooves, reminding one of cuneiform characters. 

 These deep grooves make the ribs, before referred to, jagged 

 at their margins. The lateral area is separated from the 

 pleural by a fold surmounted by extra large pustules, which 

 are widely spaced. The first three rows next the beak are 

 composed of minute pustules which quickly lose themselves in 

 the lateral rib of the dorsal area, before referred to; the fourth 

 row of pustules is composed of three minute and six large ones 

 placed diagonally in the row which is parallel to the dorsal area, 

 beyond the ninth pustule. In this row the sculpture is con- 

 fluent, forming a broad flat rib for about one-third of the 

 total length of the valve. The rest of the valve is decorat-ed 

 with five rows and one-half row of elongated, much raised, 



