4 LEPIDOPLEURUS. 



Chitons cancellatus Sows (as ? of Leach ms.~), Conch. 111. f. 104- 

 5, 1839. REEVE, Conch. Icon. t. 59, f. 152. FORBES & HANLEY, 

 Hist. Brit. Moll, ii, p. 410, t. 59, f. 3. JEFFREYS, Brit. Conch, iii, 

 p. 217; v, p. 198, t. 56, f. 1. Lepidopleurus cancellatus SARS, 

 Moll. Reg. Arct. Norv. p. Ill, t. 7, f. 6 ; t, i, f. 8. Leptochiton 

 cancellatus CPR. MS., p. 3. BALL, Proc. U. S. Nat. Mas. 1878, p. 

 315. Chiton albus PULT. not ~Linn.,fide Hanley. Chiton asellus 

 MiDD.,not of Lowe. Ch. rissoi AUCT., not Payr. / Ch. islandicus 

 GMEL., Syst., p. 3206. 



This species without careful inspection will usually be confounded 

 with small specimens of Trachydermon albus, but a glance at the 

 sculpture is sufficient to separate it. From several other species of 

 Leptochiton it is less readily distinguished, and a magnifier is indis- 

 pensable. The differential characters are as follows : 



The pustules which constitute most of the sculpture are arranged 

 like overlapping coins or a solid-linked chain in lines which in the 

 dorsal area are nearly parallel with the longitudinal axis of the 

 animal. The lateral areas are distinct, and the pustules upon them 

 are arranged in rather indistinct lines radiating toward the lateral 

 ends of the valves, at nearly right angles to the lines on the dorsal 

 area. The sculpture on the mucro is more delicate than elsewhere. 

 The apex of the posterior valve is not sunken and is not so sharp 

 as in other species compared with it here ; the girdle is scaly, with 

 also some small, spinose, transparent scales near the margin. There 

 are five gill plumes on each side, prominent and near the vent. 

 There appear to be two fenestra on each side. The lateral areas 

 and other portions of the valves are nearly always colored with 

 blackish or ferruginous patches, but these, as with Trachydermon 

 albus seem to be really composed of extraneous matter. In L.fuli- 

 ginatus Ad. & Rve., the pustules are much smaller, and while hav- 

 ing a general longitudinal arrangement on the dorsum, do not form 

 regularly defined rows or chains. The areas are not raised above 

 the dorsum. The shell is much larger and more elevated, with a 

 somewhat sunken and quite sharp posterior mucro. The other 

 mucrones are not raised but about them the sculpture is more regu- 

 larly aligned than elsewhere. I have compared the valves of a 

 typical specimen from Korea, collected by Belcher. Reeve's figure 

 of the sculpture is very bad, as are most of his details. L. alveolus 

 Sars is a very distinct species, though it has been confounded with 

 this. Its sculpture is composed of larger and rather more sparse, 



