PALAEONTOLOGY OF NEW YORK. 



feature of the direction of the aperture is inferred from the lines of growth 

 and the direction of the ornamentation of the test. The crenulations are 

 preserved as fine, rounded ridges and strise, along the internal mould of the* 

 walls of the air-chambers. 



Air-chambers frequent, regular, becoming numerous toward the apex, 

 having a depth of ten mm. near the grand chamber, and of one mm. near 

 the apex. Septa smooth, with a very slight concavity, equal to an arc of 

 about 60°. Sutures straight, and at right angles to the spiral axis. 



Siphuncle near the ventral side, small in its passage through the septa; 

 having a diameter of six mm. where the tube has a ventro-dorsal diameter 

 of forty-five mm. 



The test has a thickness of about one mm. on the outer volution. Surface 

 marked by irregular, lamellose, undulating lines of growth, which slope in a 

 retral direction, oblique to the spiral axis of the tube. The ornamentation 

 consists of strong, transverse, prominent, plicate, foliate expansions of the 

 test, inclining toward the aperture, and having an elevation of about twenty- 

 seven mm. on the outer volution, growing less prominent and more finely 

 plicated toward the apex. These expansions are quite regularly plicate, and 

 present surface-markings similar to the general surface of the tube. The 

 folds or plications are continued along the tube, forming rounded, revolving 

 ridges. The sinus in the striae and ornaments of the test is rounded, and 

 has a width equal to twice the depth. 



The internal mould is annulated from the strong transverse expansions 

 of the test, and shows the furrows and ridges of the crenulations, with those 

 of the test. Sutures not impressed. 



One specimen, nearly entire, constituting about one volution and a half, 

 has a length of 600 mm., with a diameter of seventy-five mm. near the aper- 

 ture, and measures 210 mm. from the ventral margin of the aperture across 

 the volutions. 



This species is distinguished by its size, the curvature of the tube, the apical 

 angle, and the prominence of the ornamentation. The apical portion differs 

 from G. trivolve in its more rapidly enlarging tube and marked characters of the 



