312 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



hand planato ; lam. post, super-suturalibus minoribiis, longis, ii siuibus 

 marginalilms conspicue separatis ; mn\ postico altissimo, irregulariter 

 gothico, lam. jimctis ; valvis omnibus mucronatis, mucroDe seu umbili- 

 coideo seu pnuctato seu pustuloso ; zona omnino fasciculis minutis 

 spicularum minimarum irregulariter conferte instructa. (Cpr.) Lou. 

 200, Lat. 75 mm. Div. 130°. 



Hah. — Jajian Sea ; Sakalin Id. ; Kuril Ids. ; Kamchatka (southern 

 extreme) ; the Aleutian Islands and the Vvhole coast southward to 

 Monterey and the Santa Barbara Islands, California. Usually found 

 just below tide-marks, and often cast uj) on the beach in great numbei's 

 by severe gales. Collected abvindautly at Unalashka and Sitka, also at 

 Monterey ; Dall ! 



This the largest and in many other respects the most remarkable of 

 all Chitons is readily recognized by its wholly covered valves, no indi- 

 cation of which is evident, even under the skin, in fresh examples. It is 

 covered with cells, each holding a fascicle of small spines, which, when 

 dry, have an urticating effect upon the skin of those who may handle 

 them. The foot and softer parts are used as food by the Aleuts and 

 Indians ; they are eaten in the raw state. The back is of a fine ferru- 

 ginous red when fresh ; dried specimens are usually more or less dis- 

 torted and mauled ; one of those figiu-ed by Eeeve appears to have been 

 partly rotten. 



There is a good deal of variation in the size and relative proportions 

 of the valves in ditierent individuals, and the fissures arc sometimes 

 partly abortive or abnormally multiplied. 



The soft parts of this species have formed the subject of an extensive 

 monograph by Dr. Middendorf in his first part of the Beitr. Mai. Eos- 

 sica. To that work the student is referred for details. 



Genus KATHERIXA Gray. 



JSatherina Gray, F. Z. S. 1847, p. G5. Typo K. tunicata Wood. 



Lorica parva; zona Iffivis, in suturas valde expansa; laminae valde 

 antice projectce, v. post, ssepe lobatoe; sinus altissimus, spongiosus; 

 branchiiE ambientes. 



This is an aberrant genus. In the smallness of the exposed portion 

 and smoothness of the girdle it resembles PJiacelloplcura ; in the extreme 

 anterior projection of the plates, and in the deep spongy sinus, it is most 

 like N'tittalJlna, of which it might be regarded as an exaggeration with 

 a smooth girdle ; but the tail-plate has most afSnity with the Mopaloidea. 

 Specimens may be found with many lobes Yika Phacdloplcura ; but on 

 comparison of many individuals it will bo found that the normal ai'- 

 rangement is a mopaloid slit on each side, with ah angular sinus at the 

 tail, and that the extra slits arc extremely irregular and secondaiy. In 

 NuftaUin-a, the i^lan, on the contrary, is i)erfectly regular, and Pliacello- 



