370 PALEONTOLOGY OF NEW YORK. 



Test thin, with a thickness of .75 mm. over the chamber of habitation, and 

 of .25 mm. on the apical portion of the tube. Surface marked by fine, irreg- 

 ular, lamellose lines of growth, crossed by irregular, longitudinal striae. The 

 ornamentation consists of regular, prominent, sharp, foliate ridges or expan- 

 sions of the test, slightly inclining toward the aperture, and are more distant 

 along the middle portions of the tube ; becoming gradually more numerous 

 and less prominent toward the apex and aperture. On one specimen the 

 distance between two expansions is ten mm., and on another five mm., 

 varying with the age or size of the individuals. Sometimes the elevation 

 of the folds measures nine mm., but it is only on the larger specimens. 

 Sinus very distinct, affecting the surface-markings and transverse costoe ; 

 angular near the apex, becoming deeper and rounded toward the aperture. 



The internal mould preserves traces of the furrows of the crenulations, the 

 surface-markings and low angulations corresponding to the prominent, trans- 

 verse expansions of the test. The ventral side of the tube is slightly flat- 

 tened along the portion covered by the sinus in the striae and ornaments. 



A small example, nearly entire, has a length of 193 mm., with a diameter 

 of thirty-one mm. at the aperture, and shows about forty-five of the trans- 

 verse costae. The largest individual observed has a diameter of thirty-five 

 mm. at the aperture. 



This species resembles C. amulum, but is characterized by its lesser curva- 

 ture of the tube, larger apical angle and more distant, regular and prominent 

 transverse folds, forming the ornaments of the test. It is a common and 

 well-marked species, and may be recognized, even from small fragments, by the 

 distance and prominence of the transverse expansions, which resemble those of 

 G. Matheri, but are much more frequent. In the Schoharie grit the specimens 

 are mostly very imperfect and fragmentary, but the limestones above furnish 

 well-preserved individuals, which retain their natural form and proportions 



Formation and localities. In the Schoharie grit, in the counties of Schoharie 

 and Albany, and in the limestone of the Upper Helderberg group, at Scho- 

 harie, N. Y. 



