225 



1 am inclined to ignore these sub-divisions as being insufficiently 

 defined. The length of the slit not only vanes considerably in 

 different examples of the same species, but in some it is absent ; 

 the striation is also a very unreliable character. In D. Afri- 

 cantim some specimens show only the V shaped notch, others a 

 short fissure below, while others again have quite a long fissure, 

 I have selected an average one for the type. Some of the 

 young specimens are striated towards the apex. 



Dentalium exasperatum (Plate V., fig. 12). Shell 

 moderately solid, very little curved, rather wide at the base, and 

 gradually tapering to the apex, pale yellow, longitudinally 

 ribbed ; principal ribs about 1 3, scabrous through the crossing of 

 fine transverse laminae, an intermediate much smaller rib between 

 each, the interstices being cancellated by minute longitudinal 

 ridges and fine transverse laminae. Apical fissure on the convex 

 side, about one-tenth the length of the shell. 



Length 32 ; width at the aperture 5, and at the apex i millim. 



Hab. : — Umvoti River Mouth (Natal) bearing N. by W. \ 

 W. ; distant 4^ miles ; depth, 27 fathoms. Bottom, sand and 

 shells. 



An example of the " Fissidentalinni " group of a peculiarly 

 scabrous character. 



Chiton (Hanleya) sykesi (Plate V., fig. 13). Shell 

 elongated, whitish, with the back much raised, and the sides slop- 

 ing, scarcely convex ; dorsal ridge rounded ; throughout very 

 finely granulose. Anterior valve crescent shaped, marked with 

 concentric growth lines, but no radiating sculpture ; insertion 

 plate scarcely defined, unslit. Posterior valve with apex nearly 

 central, raised, rather acute. Intermediate valves without in- 

 sertion plates ; obtusely beaked ; lateral areas well defined, 

 flattened, roughly marked with irregular concentric ridges and 

 growth lines ; central areas smooth, excepting for the fine granu- 

 lar sculpture which covers every part of the exterior of all the 

 valves. Girdle very minutely spiculose. 



Length about 22, width of central valve y\ millim. 



Cape Point Lighthouse (False Bay) bearing E. ; distant 26^ 

 miles; depth, 2io fathoms. Also Vasco ue Gama Pk. bearing 

 S. 75° E. ; distant i^^ miles; depth, 166 fathoms. 



A careful examination of the valves and girdle of this species 

 shows that it belongs to Gray's genus, Hanleya, which Pilsbry 

 places in the Family Lepidopleiiridce. Malacologists are at 

 liberty to use their own discretion as to the adoption of the 

 numerous family and generic names proposed for the Polypla- 

 cophcra, but for mv part I very much question their utility, and 

 prefer to call Hanleya a sub-genus of Chiton. 



