12 
PALEONTOLOGY OF NEW YORK . 
of these beds, but is describedjn 
the concluding pages of this work 
as L. paracletus, sp. nov., has 
afforded the most complete and 
satisfactory representation of the 
system of muscular scars. The 
pedicle-valve here figured is drawn 
from a cast of the interior, which 
shows not only the centrals ( h ), 
middle laterals (k), but the dis¬ 
tinctly specialized outside laterals 
(l), anterior laterals (j), the transmedians (i), and the great umbonal (g). 
Even the asymmetry of the transmedians (i) is apparent in the unequal 
size of the impressions, that on the left in the figure (corresponding to the 
right, when looking into the interior of the valve) being'noticeably larger than 
its correlate. In the brachial valve, the scars are essentially like those in the 
corresponding valve of L. Melie, shown in the accompanying figure, but are not 
placed quite so far back. Here the laterals (/, k ) and transmedians (i) are 
coalesced, and show a tendency to spread transversely over the visceral region, 
a feature sometimes noticeable in other palaeozoic species, and probably of 
similar nature to that seen in Barroisella subspatulata (Plate I, fig. 16). 
As far as the vascular markings of the brachiocoele in the fossil species have 
been observed, they appear to have been in full agreement with those of the 
living type. In L. Whitii, L. Elderi, L. punctata, L. cuneata, and L. lamellata the 
large pallial sinuses are to be seen passing forward from the parietal band, or 
the position of the compound lateral scars, approaching each other until they 
nearly or quite meet in front. The outer ramifications from these large trunks, 
and, in L. Elderi and L. cuneata, the inner also, are discernible. In the brachial 
valve of L. Elderi are seen the vascular impressions of the pleurocoeles, which 
lie in the post-lateral portion of the internal cavity, outside the parietal 
band. In L. Proderi and L. paracletus, the anterior vascular branches appear 
to radiate from the edge of the central muscles, as though the pallial trunks 
