286 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
small, solid, smooth scales. Gills almost ambient. (Carpenter.) Length, 
40; breadth, 26 mm.; divergence, 135°. (Tryon and Pilsbry, Manual of 
Conchology .) 
Type in United States National Museum. Type locality ? 
Range. Shumagin Islands to Puget Sound. 
Described as Trachydermon trifidus Carpenter. 
Genus CHAETOPLEURA Shuttleworth, 1853 
Valves as in Ischnochiton; eaves solid; girdle leathery, more or less 
hairy; gills extending almost or entirely to the front end of the foot. 
(Tryon and Pilsbry, Manual of Conchology.) 
Type. C. peruvianus Lam. 
Distribution. West Coast of North America. 
Chaetopleura gemmea Carpenter, 1892 
Tryon and Pilsbry, Manual of Conchology , 14:31; PI. 13, figs. 69-74. 
Shell oblong, elevated, red, olive-ashen or yellow; umbo of tail valve 
depressed, situated behind the middle. Lateral areas decidedly raised, 
coarsely radiately tuberculate; central areas having longitudinal beaded 
lirae. Girdle narrow, leathery, sparsely clothed with short hyaline hairs, 
which are readily rubbed off. The valves are elevated. The central areas 
are sculptured with elevated, distinctly beaded longitudinal cords, about 
15 in number on each side; they become very small or subobsolete upon 
the jugum. The lateral areas are strongly differentiated; they have 5 to 7 
radiating rows of distinct, clear-cut tubercles. The mucro does not rise 
above the general level of the posterior valve. Inside often tinted with red, 
often having a red or black spot at the jugal sinus. Sutural plates well- 
rounded, the sinus rather deep and angular. Anterior valve having 9-12, 
median 1, posterior valve 7-8 slits. Teeth rather blunt and stout; eaves 
not spongy, rather wide. Length, 16 l / 2 ; breadth, 8 mm. (Tryon and 
Pilsbry, Manual of Conchology.) 
Type in ? Type locality, Monterey, California. 
Range. Monterey, California, to Magdalena Bay, Lower California. 
Chaetopleura beanii Carpenter, 1857 
Mazatlan Catalogue, 197. Tryon and Pilsbry, Manual of Conchology , 14:32. 
L. t. ovata, elevata (ad angulam 110°) fusco-olivacea, seu albido caeru- 
leoque maculata; valvis intermediis valde mucronatis, interstitiis curvatis, 
marginibus subrotundatis; valva postica depressa, excavata, mucrone mi- 
nimo, superiore; jugo et areis lateral ibus indistinctis; superficie tota granu- 
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