44 PALEONTOLOGY OF NEW YORK. 



The exterior surface bears a median sinus and more or less distinct lateral 

 plications. On the interior the dental lamellae are strongly developed and 

 converge rapidly, meeting a median septum from the bottom of the valve. 

 The union consists of a lateral junction of the dental lamellae with the septum, 

 the latter continuing for a short distance beyond the point of confluence as a 

 vertical ridge, always apparent in the bottom of the spondylium thus formed. 

 At the point of union these three plates constitute a tubular chamber which 

 has no external opening in older shells, and may be filled by organic deposit.* 

 The dental plates are shorter than the septum, the latter, at its base, extending 

 beyond the center of the valve, its anterior margin being concave and its inner 

 extremity acute and produced. 



Brachial valve very shallow, with narrow, inconspicuous cardinal area Sur- 

 face plicated as in the opposite valve. Cardinal process consisting of a double 

 apophysis on the sides of which are strong, divergent crural plates The spiral 

 cones are elongate-fusiform, each coil attaining its greatest diameter just below 

 the center. They are directed obliquely upward and backward towards the 

 middle of each lateral slope of the pedicle-valve. The loop is continuous, its 

 branches being directed upward and forward, uniting at their extremities. The 

 muscular impressions comprise two oval anterior, and fainter posterior scars. 

 The surface ornamentation consists of radial plications which may cover both 

 fold and sinus ; in rare instances the lateral plications are absent. The con- 

 centric growth-lines are sometimes fine and crowded, at others distant and 

 lamellose; occasionally the surface is coarsely papillose. Shell substance 

 strongly punctate. 



Type, Calceola heterodita, Defrance. Middle Devonian. 



Observations. With the appearance of this genus in the faunas of the 

 Niagara group, comes the earliest indication of shell punctation in the spiriferoid 

 brachiopods. It has been observed that when punctation appears among the 

 Spirifers themselves, as in Martinia, Martiniopsis, etc., it is late in the history 



* In the species C. rostrata. Hall, the median septum appears to traverse the tubular chamber, some- 

 times in an; irregular way, dividing it into two lateral compartments. This structure may prove to be 

 the homologue of the unsupported tube in Syringothybis. 



