CLASS GASTROPODA 
317 
wise unsculptured except for the strong, uneven lines of growth, especially 
prominent where they traverse the ribs; not beaked. Posterior valve small, 
only about half as wide as the anterior valve; sculptured by two strong, 
oblique ribs converging to the depressed, distinctly posterior, but not mar¬ 
ginal, mucro. Interior of valves calloused. Anterior valve with 9 strong, 
distinctly cut insertion teeth, the 3 anterior concave, and all coarsely 
grooved on their outer surfaces; slits 8 in number, their porous apices 
connected with the apex of the valve by lines of minute pores. Central 
valves with wide, gently arcuate sutural laminae, scarcely if at all con¬ 
nected across the rather deep sinus; slits 1-1. Posterior valve with a barely 
indented flattening instead of a posterior sinus; slits 1-1. Eaves distinctly 
spongy. Girdle of moderate width posteriorly, broadening in front to the 
wide lobe characteristic of the genus, so that the maximum diameter of 
the animal is in the region of the head. To the naked eye or under lenses 
of moderate power the girdle appears smooth and nude over its entire 
area dorsally (that it is actually thus devoid of spines I am not prepared to 
state) save for a marginal palisade of minute hyaline spinelets, and three 
or four submarginal series of armored chaetae, the members of the inner 
series of which are conspicuously the largest and extend clear around the 
girdle, about 12 chaetae in this series encircling the anterior lobe, the 
remainder placed one opposite each suture and two directly behind the tail 
valve. The ventral surface of the girdle is clothed with very minute 
scattered spinelets, visible only under quite a high power. In dried speci¬ 
mens the girdle becomes excessively thin and leathery. The ventral sur¬ 
face of the anterior lobe shows no evident radial striation even under 
moderate magnification. Color of shell in alcohol, a warm brownish-red 
with more or less lighter painting, except the anterior portion of the head 
valve which is uniformly paler. Girdle brownish-buff, the anterior lobe 
sharply paler. Interior of shell tinted a soft salmon-flesh. (Berry.) 
Type in Berry Collection, No. 1411. Type locality, Forrester Island, 
Alaska, 15-25 fathoms. 
Range. Known only from type locality. 
Family ACANTHOCHITONIDAE 
Genus ACANTHOCHITONA Gray, 1821 
Insertion-plates thrown forward, laminated; anterior valve with five 
slits, middle and posterior valves each one; teeth long, sharp, smooth; eaves 
small; gills median; sinus deep, broad, spongy; girdle hairy, with long, 
fasciculated spiculae. (Tryon, Structural and Systematic Conchology.) 
Type. C. fascicularis Auct. 
Distribution. Europe, Africa, New Zealand, Australia, Japan, China, 
West Indies, Western America. 
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