32 
BULLETIN OF THE LABORATORIES 
about half as long as the shell. Postero-dorsal margin gently curved 
toward the sharply-rounded posterior extremity; ventral margin gently 
arcuate, more strongly rounded toward the beaks, a little below which 
the ventral surface is somewhat protruded and the margins slightly 
gaping, forming a distinct byssal opening. Surface marked by fine, 
closely arranged, radiating striae, which become faint or obsolete on 
the antero-ventral portion.” 
Moot’s run, 70 feet below conglomerate I. 
MYTILARCA OCCIDENTALIS, White and Whitfield ? 
Plate XI, Fig. i.) 
The description of this species is, like most of those in the paper 
referred to, very equivocal, without measurements and almost devoid 
of comparative proportions. 
“Shell extremely elongate, very ventricose, the diameter through 
the valves on the upper third of the shell as great or greater than the 
breadth from the ventral to the dorsal margins, becoming more com- 
pressed toward the posterior, which is abrubtly rounded. Dorsal line 
nearly straight, extending about two thirds the length of the shell. 
Ventral margin gently acuate to near the anterior where it slopes ab. 
rubtly to the beaks. Beaks terminal, obtusely pointed, umbonal prom- 
inences sub-angular. Surface marked by closely arranged, concentric 
lamellose lines, parallel to the margin of the shell.” 
Our species differs from M. fibristriatus in being more expanded 
above the umbonal prominence posteriorly, the hinge being longer 
and the greatest posterior projection lower. Length, 47 mm., height, 
17 mm. Medina county, O. 
LYRIOPECTEN NODOCOSTATUS, Sp. n. 
(Plate XI, Fig. 5.) 
Shell large, longitudinally broadly elliptical; height somewhat 
less than the length, margin regularly rounded. Valves similar ; right 
valve flat. Hinge-line straight, length over two-thirds the entire length 
of the shell. Anterior ear small, somewhat acute, rather indistinctly 
marked off from the valve, but apparently without deep byssal sinus ; 
anterior ear much larger and well defined. Surface marked by about 
