234 



I suggest that these features have been suppressed in the end valves of 

 C. adenensis, owing to the great multiplication of the ribs, because I have 

 noticed that where ribs bifurcate, no additional slits are formed. In 

 C. adenensis the ribs have been so increased with corresponding reduction in 

 size, that all trace of the position of the original ribs has been lost, and the 

 upward festooning has likewise been suppressed. With the change in the sculp- 

 ture in the tegmentum no room is left for the "festooning" under the eaves. 



I designate Lophochiton johnstoni, Ashby, as the type of this new genus, 

 the name being suggested by the fluted character of the sculpture of the end 

 valves. 



Lophochiton johnstoni, n. sp. 



PI. xvi., figs. 7 a, b, c ; pi. xvii., figs. 1, 1 a, b, c, d. 

 PI. xix., fig. S. 



Introduction. — Among the specimens collected at Carnarvon, by Mr. Worsley 

 C. Johnston, is a small chiton bearing features I have observed in no other 

 species. At first I referred it to Callistochiton recens, Thiele, which was col- 

 lected in Useless Inlet, Shark Bay, in 1905, by Drs. Michaelsen and Hartmeyer, 

 and described, but not figured, by Dr. J. Thiele on the Fauna of South-west 

 Austraha of 1911, p. 402. 



But as the specimen from Carnarvon lacks some of the more important 

 characters that distinguish the genus Callistochiton, especially the "festooning" 

 of the slits in the insertion plates, and also possesses several most striking features 

 that are not mentioned by Thiele, I have given it the name of Lophochiton 

 johnstoni, after the gentleman to whose earnest efforts we are indebted for its- 

 discovery. 



General appearance. — Broad, carinated, side slope a little curved, and valves 

 radially ribbed, as in Callistochiton; lateral areas having two ribs, median areas. 

 decorated with ribs composed of longitudinal rows of granules. Girdle broad^ 

 banded, clothed with large, flat, thin, fluted, imbricating scales. 



Colour. — Light Buff (pi. xv., Ridgway's Colour Standards) suffused with 

 a pinkish tinge near the girdle, one large and two small orange spots are present 

 on each side of the posterior margin of the anterior valve, and a similar, though 

 darker, spot at the extreme end of the tail valve. The girdle is also light buff 

 with darker bands. 



Anterior valve. — Having fourteen rays or flutes, which give to the margin: 

 a crenate appearance, these rays are hardly perceptible on the first third of 

 valve, so that in an extremely juvenile specimen they might be overlooked. The 

 whole valve is covered with small, white granules ; on the first third they seem 

 to be round, but towards the girdle they increase in size and have a tendency to 

 elongate ; the posterior margin of the tegmentum is very deeply toothed, these 

 teeth being composed of two or three elongate granules which have coalesced — 

 this feature is most marked and probably unique. The ground colour between 

 the granules in all valves is pinkish-buff ; the outer orange spot, before referred 

 to, is several times as large as either of the other two. Inside is white, teeth 

 sharp, unserrated, there are 11 slits, which are broad, straight-sided, not 

 "festooned" upwards, as in Callistochiton, teeth remarkably even and placed 

 opposite the ribs, the outer ribs and one branch of a bifurcated rib have no slits 

 opposite. 



Posterior valve. — Postmedian, shallow, sloping behind mucro very gradually 

 to the girdle. The anterior portion of this valve is decorated with white 

 granules, those immediately in front of the mucro are round, but as the anterior 

 edge of valve is approached they increase rapidly in length, becoming finger-like 



