230 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
wide, low, cardinal process, little prominent; teeth strong without but¬ 
tresses, medial septum short, very thin and high, subtriangular; brachidium 
unusually slender; pallial sinuses numerous, much branched with a medial 
trunk nearly reaching the margin. Height of average specimen, 30; 
width, 30; diameter, 17 mm. (Dali.) 
Type in U. S. N. M. Type locality, northwest of Cerros Island, Lower 
California. U. S. Fisheries Commission Station, 2983. 
Range. Catalina Island to off Point Abreojos, Lower California. 
Genus LAQUEUS Dali, 1870. 
Shell with the reflected portion of the loop attached by slender pro¬ 
cesses, on each side, to the hsemal process at or near the points where the 
two septal processes branch off to the septum. Foramen complete. It will 
be observed that the reflected part of the loop is attached by the two 
(lateral) processes, not to the septum nor to the septum processes, but to 
the haemal portions of the loop (which I have termed haemal processes) ; 
thus the two septal processes, the two lateral processes, and the “bight” of 
the neural loop, form a somewhat sinuous ring, intersected by the point 
of the septum, the haemal processes and the two sides of the neural loop. 
(Dali.) 
Type. Laqueus californicus Koch. 
Distribution. West coast of North America, Japan. 
Laqueus californicus Koch, 1847. 
Plate 17, figs. 1, 2, 3, 4. 
Chemnitz, Conch. Cab. ed. 2., p. 38; pi. 2b, figs. 21-23. 
Shell large, longitudinally oval, inflated; margins slightly sinuous. 
Dorsal valve uniformly convex, with occasionally a very slight tendency 
to depression close to the frontal margin. Ventral valve a little deeper 
than the dorsal one, with sometimes a slight indication of a mesial, longi¬ 
tudinal elevation or flattened fold; beaks incurved, truncated by a small 
circular foramen, margined anteriorly by two wide deltidial plates; beak 
ridges sharply defined, leaving between them and the hinge line a flattened 
space. Surface of valves smooth, with concentric lines of growth, shell 
perforations rather large. Colour livid yellowish brown or light reddish 
brown. Length, 2 inches, 6 lines; breadth, 1 inch, 11 lines; depth, 1 inch. 
In the interior of the dorsal valve the hinge plate is bifid; cardinal process 
inconspicuous. The septum, of small elevation, extends from under the 
middle of the hinge plate to a little more than a third of the length of the 
shell; the principal laminae of the loop, after having been attached to the 
angles of the hinge plate and giving off short curved crura, proceed a 
short distance, when they again give off two slightly oblique laminae, 
