277 



OX DIJSfOPLAX FOSSVS, n.sp., AND CHITON CRAWFORDI, n.sp., 

 FROM SOUTH AFRICA. 



By E. K. Sykes, B.A., P.L.S., etc. 



Read lOtk March, 1899. 



Seteka.l specimens of an interesting form of Dinoplax, collected by 

 Mr. Biirnup at TJmkomaas, have recently passed through my hands. 

 At first I was inclined to refer them to a variety of the well-known 

 D. (/if/as, but subsequently comparison with a young and fresh 

 specimen of that species led me to consider them as new, and 

 Mr. Pilsbry, who very kindly examined them, confirmed that opinion. 



1. Dinoplax fossus, n.sp. Pig. I. 



Shell elongate-oval, elevated, ground colour generally brown, but 

 occasionally greyish, mottled and spotted with red, chestnut, or slate 

 markings. The median valves have the lateral areas well raised. 

 The central areas are foveolate with, in addition, stab-like markings, 

 which frequently coalesce so as to produce riblets ; always with a few 

 riblets on either side of the beaks. The lateral areas are radially 

 striate, the number of the striae varying greatly. The anterior valve 

 is elevated, with similar sculpture to the lateral areas. The posterior 

 valve depressed, having the mucro posterior, and the slope behind it 

 short. Interior white, marked with brown and green. Sutural 

 plates wide, connected across the sinus. Anterior valve with 7-11, 

 median 1, posterior 7-11 slits. Girdle strong, fleshy, with many 

 small spines, and bunches of them at the sutures. Length about 55, 

 breadth about 35 mm. 



JIab. — TJmkomaas (Burnup). 



The differences between this species and D. gigas are best expressed 

 in tabular form as follows : — 



Dinoplax gigas. 



Microscopically punctate, ■with in- 

 distinct riblets on the lateral 



Girdle with bunches of spines and 

 a few scattered sinsrle ones. 



Considerably larger. 



Dinoplax fossus. 



Punctate, with stab-like markings 

 which frequently coalesce and 

 cause striffi ; riblets on laterals 

 much more distinct ; a group 

 of small riblets each side of the 

 beaks. 



Girdle densely clothed with spines, 

 which form groups at the 

 sutures. 



Mr. Sowerby recorded ' the occurrence in South Africa of Chiton 

 lyratus, Shy. ; in noting this ^ I expressed the opinion that the species 



1 Journ. Conch., vol. vii, p. 373. 



^ Proc. Malac. Soc, vol. i, p. 135, footnote. 



