206 NEW YORK STATE MUSEUM 



To this diagnosis of this large and fine species should be added (a) the 

 more conspicuous development, specially in early stages, of the median 

 stria on the ventral valve, less frequently such a stria or even median sinus 

 on the dorsal valve, (d) the prominence of the dental sockets running nearly 

 parallel to the hinge and extending two thirds the distance to the cardinal 

 angles, (c) the bifurcate cardinal process, each branch of which is divided 

 in half, {d) the pustulose character of the interior of the dorsal valve ; in 

 early stages single rows of pustules arranged upon the internal striae pre- 

 sent themselves but these simple lines become confused in later growth and 

 the surface assumes low radial folds over the pallial region, (e) the absence 

 of defined muscle scars on either valve. 



The enlarged median stria is a dependable feature In determining the 

 young forms of the shell with which the rocks abound; the accompanying 

 depressed convexity, almost flatness of the valve, serving to distinguish 

 them from C h. a n t i o p a. 



Localities. Found in great quantity in the lower strata on Dolbel 

 brook i^ mile above the shore ; Shiphead, Cape Gaspe, 300 feet below 

 lighthouse. This horizon is near the base of Logan's no. 8. Elsewhere 

 the species is rare, Billings's locality was Perce Rock, and here the species 

 occurs in extraordinary abundance and constitutes the leading member of 

 the entire fauna where it is also extremely common. 



Observations. Embedded in the rock at Shiphead was found a small 

 conical mass of very young shells of this species, the base of the cone 

 upward. Some hundreds of shells seem to have been involved in this mass 

 where was doubtless a small eddy on the bottom which produced a conical 

 depression and in which the revolving water caught and whirled the Cho- 

 netes. The center of this cone is sediment, the shells being thrown toward 

 the periphery. 



Chonetes melonicus Billings 



Plate 46^ figures 1-4 



Chonetes melonica Billings. Palaeozoic Fossils. 1874. v. 2, pt i, p. 15, 

 fig. 6a-d 



Original description. Shell of medium size, usually about ten or twelve lines wide; 

 length between one half and two thirds the width; hinge line equal to the greatest width 

 of the shell; cardinal angles usually 90°, often a little less or more; all the front two thirds 

 of the shell uniformly rounded, sometimes with the front margin only very gently convex. 

 Ventral valve usually strongly convex and often extremely gibbous, always more or less 

 flattened toward the cardinal angles; area rather narrow, sometimes lying in the plane of 

 the lateral margin, but more often, owing to the strong curvature of the upper part of the 

 valve, partially inverted; foramen a little wider than high, closed by a convex deltiditim; 

 lower edge of the area in detached valves crenulated or serrated with small teeth, of which 

 there are six or seven in one line; these teeth not visible when both valves are united; 

 when the shell is well preserved and semitranslucent, faint, dark lines can be seen beneath 

 the surface of the area, as if it were penetrated by internal small tubes, passing from the 

 teeth towards the cardinal edge, and inclining a little towards the beak; umbo moderate, 



