44 
BULLETIN OF THE LABORATORIES 
regular, somewhat umbricated about the beaks. Length, .50-.60; 
width, ,30. 
This species resembles rather closely L. melie, Hall, but is not 
narrowed toward the beaks as much as in that species, neither has it 
the rather prominent mesial sinus. Our species is more oblique in 
front. 
The European L. mytiloides is also very similar, but seems to be 
uniformly smaller and more nearly resembles L. melie than our speci- 
mens. Named for the discoverer Mr. Wm. G. Tight, of Granville. 
We have thought this a possible variety of L. umbonata, Cox, a shell 
common in the coal-measures. It is nearly of the same size, but is 
relatively longer and the margins do not approach each other above as 
rapidly. It is quite characterisdc of our species that the breadth of 
the shell at one-fourth the length from the beaks is equal or even greater 
than the width at the same distance from the front margin. The oc- 
currence of this Lingula in cannel coal along with broken fern fronds 
supports the theory that it was formed under water by debris brought 
in by streams or otherwise. 
Athyvis suhtilata, Hall, 
(Plate I, Fig. 18.) 
'This common and widely distributed species seems not to be 
abundant in the rock under consideration, only a few specimens hav- 
ing been secured. 
Shell somewhat ovate, longer than broad, front margin nearly cir- 
cular; valves very nearly equally inflated; ventral valve rather more 
convex, the greatest convexity being one-third the distance from the 
prominent arched beak; mesial sinus obscure, except toward the front 
of the valve, hypodermis marked with radiating lines which sometimes 
appear through the shell, especially that at the bottom of the sinus ; 
epidermis marked by concentric lines of growth ; dorsal valve uni- 
formly convex, without evident fold and with short approximated beak. 
The radating lines on the dorsal valves are less regular — they are 
simply lines impressed upon the shell by the viscera. 
Spirifera opima. Hall. 
(Plate ir. Fig. 23.) 
Shell rather small, moderately convex, nearly semi-circular to 
