1894.] NATT'KAL SCIENCES OF PHILADELPHIA, 



73 



Isohnochiton (Haploplax) lentiginosus Sowb. 



Shell rather thin, oval, moderately elevated, carinated, the side- 

 slopes straight. Surface smooth except for slight radial riblets ou 

 the lateral areas. Ground-color orange, orange-broivn, or even Avith 

 an olive suffusion, coarsely spotted throughout xoith bright blue; the 

 girdle olive-green, iinicolored or with dusky bars. 



The intermediate valves are slightly concave behind, the beaks 

 slightly projecting and interrupting the curve. Lateral areas slightly 

 raised, marked by 4 to 6 weak, low radial riblets, obsolete in some 

 specimens. Central areas having slight growth lines, but otherwise 

 unsculptured except for the usual microscopic granulation of the whole 

 surface. End valves showing traces of radial riblets toward the 

 periphery. Posterior valve having the rather blunt mucro at the 

 summit of the straight posterior slope, and in front of the middle. 



Interior roseate in the cavity, olivaceous liehind the valve-callus, 

 the sutural and insertion- plates blue-white. Sutural-lamime short, 

 projecting less than half the length of a valve, separated by a rather 

 narrow, hardly squared, sinus. Anterior valve having 11, inter- 

 mediate valves 1-1, posterior 13 slits; teeth sharp, normal. 



Girdle clothed with densely imbricating convex, polished scales, 

 which generally show a very minute striation under the compound 

 microscope. The scales measure: width -28, alt. about -22 mm. ; 

 the width of a scale is therefore contained about 3 2 times in a milli- 

 meter. 



Length 19, breadth 10 mm.; divergence about 115°. 



This species was described from Newcastle, N. S. Wales. It has 

 since been confused with /. cyaneopunctatus Krauss, a very similar 

 species from the Cape; and its Australian habitat has been doubted. 

 The rediscovery of the species in Australia (Port Hacking, N. S. 

 Wales) by Dr. Cox is therefore of unusual interest. 



In some specimens there is a narrow whitish stripe on the ridge of 

 valves iii, iv, v, vii and viii; and in some the blue spots become en- 

 larged and diluted on valve iv, forming a pale blue or whitish varie- 

 gation. 



This cannot be Chiton clypeus Blainv. (Diet. Sci. Nat., xxxvi, p. 

 540), which is also described as blue-spotted. 



Genus CALLISTOCHITON Cpr. 

 Callistochiton antiquus Eeeve. 



Port Jackson (Cox). Readily recognized by the very strong 



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