37G PALJEOSTOLOOY OF NEW YORK. 



This is evidently the species recognized by Prof. Eaton, in his Geological 

 Text-Book, as the Orthocera paradoxica of Sowerby, — the locality cited as Beth- 

 lehem caverns, being at Clarksville, in the town of Bethlehem, Albany county. 



Formation and localities. In the limestones of the Upper Helderberg group, in 

 the Helderberg mountains, Schoharie, Oneida and Onondaga counties, N. Y. 



Gyroceras laciniosum, n. sp. 



PLATE I. II A, FIG. 8, AND SUPPLEMENT. 



Shell discoidal, openly coiled, making not less than one volution and a half. 

 Transverse section elliptical ; lateral diameter the longer, the two diameters 

 being in the ratio of four to five. Apical angle about 10°. 



Chamber of habitation not observed. Crenulations preserved as low lon- 

 gitudinal ridges on the internal mould. Aperture unknown. 



The air-chambers, septa and the characters of the siphuncle have not been 

 observed, on account of the imperfect material. 



The test has a thickness of about .5 mm. Surface marked by fine, irregu- 

 lar, undulating, lamellose lines of growth, crossed by broad, shallow, longi- 

 tudinal furrows, of which there are three in the space of ten mm. Test 

 ornamented with regular, distant, raised, foliate expansions, slightly inclin- 

 ing toward the aperture, and regularly plicated, the plications extending and 

 forming the furrows on the general surface. The transverse plicae have an 

 elevation of about six mm., decreasing in height toward the apex. The 

 sinus forms an abrupt deflection in the surface-markings and ornamentation. 



Internal mould characterized by distinct annulations, corresponding to the 

 transverse expansions of the test. 



One incomplete fragment has a diameter, measured across the disc, of 

 sixty mm., and a lateral diameter to the tube, at the larger extremity, of 

 about thirty mm. 



This species is distinguished by its transverse section and regularly and 

 deeply plicate expansions of the test. The transverse section is conspicuously 

 different from G. trivolve, and the expansions are more elevated and distant. It 



