CLASS GASTROPODA 
285 
valvis ultimis strigis radiantibus, areis centralibus strigis longitudinalibus, 
parallelis; mucrone parvo; marginibus valvarum subrotundatis, suturis 
modicis; limbo squamoso, squamis oblongis, irregulariter tessellatis; intus 
valvarum marginibus haud valve arcuatis, sinu lato, haud alto; ad jugum 
linea impressa. Long., 1.1; lat., .58; alt., 25 poll. (Carpenter.) 
Shell oblong, elevated, dorsally carinated, the side-slopes straight. Sur¬ 
face appearing almost smooth to the naked eye. Color a uniform olive or 
slaty-blue, the girdle having more or less of a blue or purple “bloom.” The 
lateral areas are very little raised, and are sculptured with numerous deli¬ 
cate radiating threads, occasionally branching toward the lower margin, 
and freely branching along the posterior edge of the valve. The terminal 
valves have similar delicate radii. The central areas have numerous longi¬ 
tudinal, somewhat beaded threads, separated by flat intervals. The pos¬ 
terior valve is elevated, with anterior umbo. The interior is light blue. 
Sutural plates low, connected across the sinus by a narrow plate which is 
sulcate above and cut into about 10 teeth by delicate slits. Anterior valve 
having 14-16, central 2-3, posterior 22 slits. Teeth even and sharp, 
slightly striated or grooved outside. Eaves solid. Girdle wide, flat, covered 
with solid, regularly and closely imbricating striated scales. Length, 35; 
breadth, 19 mm. (Tryon and Pilsbry, Manual of Conchology .) 
Type in Museum Cuming. Type locality, Monterey, California. 
Range. Mendocino County to Monterey, California. 
Described as Chiton regularis Carpenter. 
SECTION TRIPOPLAX Berry, 1919 
Ischnochiton trifidus Carpenter, 1864 
Supplementary Report, British Association for the Advancement of Science, 649. 
Tryon and Pilsbry, Manual of Conchology, 14:141; PI. 18, fig. 40. 
Center-punctures few, deep: 2-4 blunt ribs: side plates with 2 slits. 
(Carpenter.) 
Shell rather large, rather elevated, regularly oval; red-chestnut, macu¬ 
lated with lighter and darker; jugum acute, gothic. Mucro median, flat; 
entire surface very minutely granulated; central areas having about 8 
strongly punctate lines perpendicular to the jugum; lateral areas strongly 
defined, having 2 to 4 obsolete ribs, sometimes punctate in the interstices. 
Interior whitish flesh-colored, with two reddish-purple rays diverging from 
the flat umbones; posterior valve having 13, anterior 13, central valves 2 
slits; teeth acute, sometimes serrated at the edge, sometimes striated out¬ 
side, sometimes smooth. Eaves sub-spongy; sinus small, laminate, the 
laminae slit at the sides and sometimes in the middle. Girdle having very 
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