294 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Callistochiton decoratus (Carpenter) Pilsbry, 1892 
Tryon and Pilsbry, Manual of Conchology, 14:269; PI. 58, figs. 17-20. 
Shell oblong, moderately convex, obtusely subangular along the dorsal 
ridge, the side-slopes slightly convex. Surface rather shining, varying in 
color from olive-buff to dark green, uniform or having darker flammules 
and spots. Apices of the median valves eroded. Lateral areas raised, each 
rendered bicostate by a central sulcus, and having a few uneven longi¬ 
tudinal impressed grooves, giving it a terraced aspect. Central areas having 
numerous parallel longitudinal ribs, the intervals closely latticed across, 
this sculpture obsolete on the ridge, where there is a broad V-shaped 
smooth area, which rarely shows a few diverging subobsolete ribs. An¬ 
terior valve having 11 rounded ribs. Posterior valve less elevated than the 
anterior, highest at the front margin, the mucro depressed, post-median; 
posterior area having 9-10 rounded ribs. Interior bluish, generally marked 
with olive or green at jugum, bases of the sutural-plates, and slit-rays. 
Sutural plates wide, separated by a square sinus notched at each side. 
Anterior valve having 9 or 11, central 1, posterior valve 9-12 slits; teeth 
rather sharp, smooth; slit-rays distinct and porous. Eaves narrow. Girdle 
narrow, ashy-brown, covered with minute, striated, closely imbricating 
scales. Length, 20; breadth, 9-10 mm.; divergence, about 110°. (Tryon 
and Pilsbry, Manual of Conchology .) 
Type in Academy of Natural Sciences, Philadelphia, No. 118687. Type 
locality, Todos Santos Bay, near San Tomas River, Lower California. 
Range. Santa Barbara, California, to San Tomas River, Lower Cali¬ 
fornia. 
Callistochiton decoratus infortunatus Pilsbry, 1892 
Tryon and Pilsbry, Manual of Conchology, 14:266; PI. 59, figs. 37-42. 
Shell large, regularly ovate, the dorsal ridge obtuse; valves arcuate; 
mucro obtuse, median. Olivaceous, sometimes spotted with paler on the 
ribs and jugum. Central areas having about 12 parallel lirae on each side, 
decussated, the interstices having square depressions. Lateral areas having 
two very strong rounded tuberculose ribs. Anterior valve with 9, posterior 
with 7-8 elegantly spreading ribs. Interior: posterior valve having 7-8, 
central 1, anterior 9 slits; teeth concave outwardly, obtuse, slit at the apices 
of the ribs, sometimes with an intercalated slit or abnormally serrate; teeth 
of posterior valve very obtuse, hardly sloping; eaves small, delicate. Sinus 
wide, flat, but little angular, sometimes crenulated by the riblets of the 
exterior. Girdle irregularly imbricated with flattened scales, each one about 
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