304 MOPALIA. 



some valves or parts of valves vivid scarlet (fig. 64), or scarlet 

 mixed with olive and snow-white, or entirely white ; or (3) light 

 olive-buff with brownish girdle (fig. 67). 



Valves somewhat beaked, the lateral areas bounded by a riblet, 

 rather coarsely granulated, with larger granules along the posterior 

 margin. Central areas sculptured with longitudinal, curving rib- 

 lets somewhat granulated, much closer and finer on the dorsal 

 ridge. Anterior valve having granose narrow radii, the intervals 

 granulated. Posterior valve small, with posterior mucro, broadly 

 emarginate or waved at the hinder margin. 



Interior bluish-white or light blue-green. Sinus broad and rather 

 rounded, spongy or roughened. Sutural plates arcuate. Anterior 

 valve having 8 slits, median valves 1 slit. Posterior valve having a 

 broad deep, rounded caudal sinus, and a single slit on each side. 



Girdle wide, yellow or brown, generally notched behind, more or 

 less sparsely clothed with curling strap-like brown hairs, which bear near 

 their bases a bunch of minute, white, acute spines (fig. 66; the line 

 below is 1 mill. long). 



Length 46-50, breadth 25 mill; divergence 125. 

 Unalashka, Aleutian Is. (small and rare) to Sitka, and southeast- 

 ward to Monterey, California; low water to 20 fms. on stones and 

 shells. 



Chiton ciliatus SOWERBY, Ann. and Mag. Nat. Hist. 1840, p. 

 289 ; Conch Illustr., f. 79 (1840). Not Chiton ciliatus Reeve, nor 

 Mopalia ciliataDall. Chiton wosnessenskii MIDD. Bull Acad. Imp. 

 Sci. StPetersb. iv, p. 119, 1847. Chiton (Hamachiton, Platysemus) 

 wosnessenskii MIDD., Mai. Ross., i, p. 34, 101, t. 11, f. 1-2. Mopalia 

 kennerleyi CPR., Suppl. Rep. Brit. Asso. Adv. Sci. 1863, p. 648 ; 

 Proc. Acad. Nat. Sci. Phila., 1865, p. 59. M. (kennerleyi var.} 

 Swannii CPR., Ann. Mag. N. H. xiv, p. 426, 1864; Suppl. Rep. B. 

 A. p. 648. Mopalia grayi CPR., L c. p. 603 (name only). Mopalia 

 wossnessenskii Midd., DALL, Proc. U. S. Nat. Mus. 1878, p. 305 

 (1879). 



This species is distinguised from M. muscosa and its immediate 

 allies by its color ; by the lack of that narrow anterior projection 

 of the outer layer at the sinus, so conspicuous in the detached 

 valves of the typical muscosa; by the encroachment of the wide gir- 

 dle at the sutures, the deeper caudal wave of the tail valve, and 

 especially by the broad, rounded sinus between the sutural plates. 



