44 NATURAL HISTORY OF KERGUELEN ISLAND. 



Patella ? delessertii, Philippi. 

 Mus. No. 11902. 



Straits of Magellan, authors ; Kergueleu, one dead specimen 



probably of this species, Dr. Kidder. 



CHITONID^. 



Genus HEMIARTHRUM, Cpr., MS. 



Valvae terminales laminatse, hand articulatse, laminae laterales obso- 

 letse ; zona lanuginosa, porifera ; branchiae posticae. 



HEMIARTHRUM SETULOSUM, Cpr., n. S. 



Mus. No. 11903. 



H. t. latiore, curvata, olivaceo-fusca; jugo planato; mucrone sub- 

 centrali ? areis baud defluitis ; tota superficie sensim quincunxiter 

 granulosa, granis satis extantibus. 



Intus ; valva antica et postica conspicue lamiuata; laminis acutis, 

 baud iucisis, baud regularibus, valde extantibus ; subgrundis spongi- 

 osis, minimis; valvis centralibus et postica laminis suturalibus, tri- 

 angularibus, maxime distantibus, extantibus, decliviterlateraliter, conti- 

 nuis; sinu maximo, valde spongioso. 



Zona modica, baud exi^ansa, solida. leve; sparsim minutissime lanu- 

 ginata; poris miuutissimis, setuliferis ad suturas, et circ. iv. circum 

 valvas terminales sitis, instructa, setulis minimis, curtissimis. 



Animal, pede capiteque normalibus; branchiis majoribus posticis, 

 utroque latere circiter vi, medio pede tenus. Lon. IS*"™. Lat. 7™™. 

 Div. variaute ad 130°. 



Kergueleu Island, on stones at low water, Dr. Kidder, two specimens. 



This shell, externally, resembles some of the coarse, ill-defined acan- 

 thochitons. The girdle, however, is narrower and smoother than in 

 that genus, and the pores so extremely minute that in a dry specimen 

 they would escape attention. Within, however, the features are entirely 

 new, though not unexpected. It forms a transition between Hanleia 

 {mendicaria) and the articulate chitons. A single unslit lamina sur- 

 rounds both the terminal valves, projecting far beyond the external 

 layer. In the posterior plate this is continued forward to forai part of 

 the sutural laminae. These, in all the valves, slope off, both toward the 

 middle and toward the sides, so as to take the place of the ordinary 

 side-laminae, which here do not exist. 



The specimen examined — hardened by preservation in alcohol and 



