340 THE PALEONTOLOGY J.OF MINNNSOTA. 
LLingula elderi. 
and still finer radiating lines. These give to the surface a minutely crenulated 
appearance; also several distinct radiating lines over the anterior half of the valves 
which interfere somewhat with the rounding of the concentric lines. 
'"In the dorsal valve the impressions of the pallial sinuses [vs] are deeply 
marked and are widely separated, leaving the area within them very considerable; 
the central or inner ramifications [v] are very distinct, and the outer ones also for a 
short distance from the main branches, while the posterior branches show the 
lateral ramifications only on the outer side. The divaricator [umbonal] muscular 
scar of the dorsal valve [g] is very large and curved forward at the sides, being sit- 
uated well back near the apex of the valve. It cannot be positively traced on the 
ventral side, most of the specimens being imperfect at this point. The anterior 
adductor [anterior laterals] scars [j] are small and situated near the center of the 
valve, while the posterior adductors [h, central scars] are large and situated outside 
of and posterior to them so as to inclose their posterior ends. The adjustor [lateral, 
middle and transmedian] muscles [1 i k] are distant from each other, and placed just 
within the posterior third of the length of the shell. Two elements can be detected 
in each scar on some individuals, but they are usually obscure. 
"On the ventral valve the lines of the pallial sinuses are nearer together on the 
anterior half of the shell than on the dorsal, the same as shown in L. anatina, but 
spread out rapidly toward the middle, and, on the posterior half, occupy nearly the 
same relative position as on the other side. Near the center of the valve are seen a 
pair of large [central] scars [h], which have advanced from behind their track, 
forming a strong feature on the cast, as it originates just in front of the position of 
the divaricator [umbonal] muscular scar [g], and gradually widens as it advances 
until it occupies fully one-half of the width of the cast near the middle of its length. 
In the central line of these scars there is an elevated ridge, which terminates in a 
slightly prolonged tongue, and seems to represent the central adjustors [middle 
laterals, k]. The large scars outside of these are probably the posterior adductors 
and external adjustors combined. Posterior to these and distant from the median 
line are other scars, which are long and narrow, which have also left their track as 
they have advanced. Two elements are represented on each side, and mark the 
place of the posterior adjustors and anterior adductors [anterior, laterals and trans- 
medians, j i]. Between the lines formed by the advance of the scars of the adjustor 
muscles and those of the central area, on each valve, there is a nan-ow smooth 
impressed space which unites with the line of the pallial sinuses at the junction of 
the anterior and posterior branches, seen on all the specimens, and for which I have 
not been able to satisfactorily account, as it lies within the area of the muscular 
scar, and consequently within the walls of the perivisceral chamber. The areas of 
