MOPALIA. 295 



M. MUSCOSA Gould. PI. 63, figs. 46-48 (typical), figs. 49-63 (varr). 



Shell oval, elevated or depressed, the dorsal ridge more or less 

 angular. Valves strong. Surface lusterless, finely sculptured with 

 wavy, crenulated logitudinal riblets, often more or less obsolete. 

 Color generally dull brown, blackish-olive or grayish, but sometimes 

 bright orange, scarlet or vivid green. 



Median valves hardly beaked, the lateral areas slightly raised, 

 granose, limited by a raised granose riblet. Central areas having 

 close fine longitudinal riblets, with crenulated or latticed interstices, 

 the riblets finer and converging on the ridge of the last 6 valves, 

 diverging on the second valve, or strongly diverging on the ridge of 

 all valves, like a series of superimposed v's. Anterior valves having 

 about 10 narrow radiating granose riblets, the intervals granose. 

 Tail valve depressed with posterior mucro, the posterior slope very 

 short, emarginate behind. 



Interior bluish-green, stained with lilac on the central callus. 

 Anterior valve having 8, median 1 short slit, the teeth long, deeply 

 striated outside and thickened or propped outside at the sides of the 

 slits. Posterior valve having a rounded sinus behind, with one 

 oblique slit on each side, the plate roughened outside near the slits. 

 Sutural plates broad, the sinus extremely shallow and small. 



Girdle rather narrow, densely covered with round, curved or 

 curled hairs. Gill row as long as the foot (pi. 64, fig. 74). 



Length 52, breadth 38 mill. 



Length 25-60, breadth 15-40 mill. ; divergence 120-140. 



Shumagin Is. (rare) to San Diego, California, between tide marks 

 and at lowest water. 



Ch. muscosus GLD., Proc. Bost. Soc. N. H. ii, p. 145, July, 1846 ; 

 Exped. Moll., p. 313, f. 436 ; Otia, p. 6. Chiton ciliatus REEVE 

 Conch. Icon., t. 19, f. 124,Mopalia ciliata H. & A. AD. Gen. Rec. 

 Moll., i, p. 478. DALL, Proc. U. S. Nat. Mus., 1878, p. 303 (syn- 

 onymy and variation) ; p. 298, f. 35, 35a (dentition). NOT Ch. 

 ciliatus Sowerby ! Chiton setosus So WE. in Beechey's Voy. 'Blos- 

 som' p. 150, t. 41, f. 17 (not C. setosus Sowb. 1832). Ch. collei 

 REEVE, Conch. Icon., t. 21, f. 136 (1847). Ch. wosnessenskii 

 MIDD. Mai. Ross, i, p. 101 (part of diagnosis). Chiton armatus 

 NUTT., JAY'S Catalogue, 1839, no. 2678 (not described) ; Ch. arm- 

 atus NUTT., in Mus. Acad. Nat. Sci. Philadelphia. C. ornatus 

 NUTT. MS. CPU., P. Z. S. 1855, p. 232. and C. consimilis NUTTALL, 

 MS. in Brit. Mus. 



