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DESCRIPTION OF ONITHOCHITON (?) ISIPINGOEXSIS, n.sp., 

 FROM SOUTH AFRICA. 



By E. B. Sixes, B.A., F.L.S., etc. 



Read \Uh June, 1901. 



Onithochiton (?) Isipingoensis, n.sp. 



Shell moderately elongate. Valves somewhat elevate and bluntly 

 keeled; dorsal area green; other areas pale pink, a slight yellow 

 tinge marking the junction with the dorsal area ; girdle dark red, 

 narrow behind, and somewhat produced in front, with apparently 

 eighteen very small tufts of spines. Intermediate valves somewhat 

 convex behind, very slightly concave in front. Dorsal area wedge- 

 shaped, well separated from the side areas, smooth to the naked eye, 

 but showing transverse markings under a lens. Latero-pleural areas 

 showing no trace of any division, sculptured all over with large, 

 unequal, flattened tubercles. The anterior valve is similarly sculptured. 

 Posterior valve similarly sculptured, but having a dorsal area ; it is 

 concave above and the mucro is posterior. Interior of valves pale 

 pink. The anteiior valve has six slits, but probably the normal is five, 

 the median valves one, teeth pectinate. The insertion plate of the 

 posterior valve is flattened behind, and appears to be without any 

 slit, the tegmentum overhanging and the valve being obtusely beaked 

 behind. Probably the mollusc when alive was about 15 to 20 mm. in 

 length. 



Onithochiton Isipingoemis, n.sp. 



Hab. — Isipingo, South Africa (coll. Burnup). 



A very puzzling species, as to the true generic position of which 

 I am somewhat in doubt. The general facies recalls Acanthochites, 

 but the peculiar form and structure of the posterior valve leads me to 

 refer it to Onithochiton. 



