398 



than being strictly longitudinal, and the outer margin, are 

 a few irregularly-placed elliptical or rounded pustules, some 

 milk-white, others dark. Inside white, slits one, ill defined, 

 and placed far back on the insertion plate, suture broad. 



Hab. — Marino, South Australia. Collected by myself; 

 only one specimen on rocks at low tide. 



Girdle. — Spongy, but in places scattered minute spicules 



can be detected, towards the outer margin there are evidences 



of minute scales; it is possible that the scales have broken 



away from the older parts of the girdle. A fairly conspicuous 



.hair-tuft is placed at each suture, but the spicules are short. 



Measurement. — 7 mm. x 3 mm. 



Remarks. — This beautiful and striking Acanthochiton is 

 easily distinguished from any known species by the row of 

 exceptionally large milk-white pustules suggesting a row of 

 rounded teeth set in a jaw, present in the median valve. The 

 name is derived from the Latin maxilla, a jaw. The type I 

 am for the present keeping in my own collection, but ultimately 

 I hope to place it in the South Australian Museum. 



Acanthochiton gatliffi, n. sp. 

 PI. xlii., figs. 2 to 5. 



General ajrpearance. — Shell twice as long as broad (dried 

 specimen), side slope very slightly curved, dorsal area broadly 

 wedge-shaped, much raised, rounded transversely and longi- 

 tudinally, valves covered with curved longitudinal rows of 

 rather large, raised, flat pustules. 



Colour. — The dorsal areas are deep Hellebore red, and the 

 girdle and most of the ground-colour of the rest of the shell 

 Dresden brown, the red merging into the brown ; the pustules 

 are a lighter shade than the portion of shell on which they are 

 placed. (Bidgway's Colour Standards, pis. x., xxviii., and xv.) 



Anterior valve. — Five rays or undulations, the whole 

 valve uniformly clothed with whitish, elliptical, raised pustules, 

 well separated from one another but not placed in defined 

 rows ; these pustules are smaller and less flat than are those on 

 the median valves. Inside and insertion plates deep pink, 

 five slits, teeth sharp. 



Posterior valve. — Very small, mucro slightly posterior, 

 dorsal area wedge-shaped but smaller in proportion than the 

 other valves. The portion of shell to the front of the mucro 

 is ornamented with a few large flat pustules in two rows, the 

 posterior portion of valve decorated towards its margin with 

 two rows of small granules. Inside pink, slits three, the 

 insertion plates are produced posteriorly for a width almost 

 equal to half of the exposed portion of valve, sutural laminae 

 are produced sideways to an unusual degree almost forming 

 a point, sinus broad. 



