Acanthochites.] AMPHINEURA. 29 



agrees in having 5 prominent lobes on the anterior valve, the ribs 

 being of white raised elongated granules, the ribs of all valves similarly 

 marked ; another characteristic feature is the presence of 3 almond- 

 shaped white granules just within the posterior edge of each median 

 valve. Dorsal areas wedge-shaped, the edges being serrated, sculp- 

 tured with cuneiform lyrula?. The posterior valve has the tegmentum 

 longer than the breadth, the hooked mucro being slightly post-median ; 

 the area behind it is concave, white, composed of oblong granules, 

 bordered on either side by others of longer form but the same colour. 

 Anterior valve with 5 slits corresponding to the ribs ; median valves 

 with 1 slit ; posterior with many slits, the denticles being mostly 

 bifid. In the type these denticles are perpendicular, and not visible 

 from above ; in other specimens they extend outwards, and may 

 be seen beyond the tegmentum ; in such specimens the mucro is not 

 so prominent, the white area narrower, and composed of long granules 

 like those bordering the oblong granules of the type, these latter being 

 altogether absent, as also are the raised white borders of the valves. 

 It may be that these specimens have not attained their full develop- 

 ment, as none of them approach the type in size. Interior blue-green, 

 white towards the edges. Girdle grey-green, leathery, a minute pore 

 at each suture, 4 on anterior valve. (Webster.) 



Length of dried specimen, 35 mm. ; width, 18 mm. 

 Type in Mr. Webster's collection. 



Hob. Orua Bay, Manukau Harbour, on rocks at low tide ; Manu- 

 kau Harbour, in 4 fathoms (Captain Bollons). 



Remarks. The type is unique ; seven of the less-developed speci- 

 mens were found. The apparent hybridism is striking, especially 

 as I have never found A. violaceus on the west coast, though a very 

 small form of A. zelandicus is fairly common. (Webster.) 



4. Acanthochites rubiginosus, Hutton, 1872. Plate 4, fig. 4. 



Tonicia rubiginosa, Hutt.. T. N.Z.I., iv, 1871 (1872), 180. Acanthochites 

 rubiginosus, Hutt., J. Mai., xii. 68, pi. 9. f. 12-17. A. costatus, Ad. & 

 Ang. : Suter., P. Mai. S.. ii, 194. not Ad. & Ang. Plaxiphora terminates, 

 Smith: Wissel, Zool. Jahrb., xx, (309, pi. 21, f. 22; pi. 23. f. 23, 24 

 (anatomy) ; not of Smith. 



Shell oblong, small, subcarinate, the whole surface granular, mostly 

 yellowish-pink, girdle with minute spines and sutural tufts. Anterior 

 valve with 5 ribs, which are not very conspicuous ; the whole surface 

 granulated, the granules being largest and sometimes unequal in shape 

 near the margin, and decreasing in size toward the apex of the valve, 

 which is slightly sinuated. Intermediate valves with the jugum sparsely 

 longitudinally substriated ; the pleura! tracts are granular, divided 

 into central and lateral areas by a low granular rib, the granules pebble- 

 like near the margin, diminishing in size very rapidly toward the 



