163 



bb. Surface sculptured with riblets. 



c. Ribs stroug and coarse ; colour black-olive, uni- 

 form sulcatus Wood. 



cc. Riblets fine; colour variegated. 



d. Riblets of central areas nearly obsolete, of 



lateral areas granose barnesi Gray. 



dd. Riblets of central areas fine, distinct ; sbell 



olive mottled with dark . . virgulatus Sow. 



aa. Scales of the girdle irregular chierchiae Nierstr. 



IV. On Isclinocliiton rissoi Payr. and its afflnities. 



(Fig. 10—14). 



In H. A. Pilsbry's Man. of Conchol. Vol. 14, Pag. 102 we 

 find a detailed description of Ischnochiton rissoi Payr. with 7 

 figures, taken from Issel's Study on the Chitons of the Sea of 

 Genoa. As varieties of this form Pilsbry mentions Ischnochiton 

 meneghini Cap. and Ischnochiton fragilis Monts. Now we read in 

 the Nautilus, Vol. 12, n^. 5, 1898, Pag. 52 a short article by 

 C. F. Ancey on : » Marine Shells collected at Port Gueydon, Kabylia, 

 with description of a new Cyclostrema" , In this article Ancey 

 mentions a new Chiton, which is called by him Lepidopleurus 

 dautzenbergi as a variety of Lepidopleurus meneghini Cap. 



Two years ago,. when on a visit to the Zoological Station at 

 Naples, I collected a good number of Chitons, among which I 

 found several specimens of Ischnochiton rissoi Payr., meneghini 

 Cap. and, no doubt, also of dautzenbergi Ancey. I examiued these 

 animals carefully with the intention of investigating, whether we 

 have here distinct species or varieties of one species. 



Pilsbry's description of the valves of rissoi is exact. According 

 to him the surface of the valves is »longitudinally lirate; the 

 lateral areas are moderately raised and sculptured with coarse, 

 flat, uneven-edged longitudinal riblets, which are separated by 

 narrow punctate intervals and are frequently irregular. The central 

 areas have close, fine riblets in the same direction, somewhat 



