24 NEW YORK STATE MUSEUM 



in its greatly extended spirals, low, narrow and numerous whorls (13 in the 

 typical specimen), very direct and transverse sutures. The shell is extremely 

 uncommon in New York but in the Dalhousie fauna it is one of the abun- 

 dant species and no doubt exists of the specific identity in the two localities. 

 The original is a palpable internal cast ; those at Dalhousie usually retain 

 the external markings and these show that the shell is wholly without exter- 

 nal evidence of a slit band, while the surface is otherwise quite smooth 

 and bears simple concentric growth lines. Like the shells we have referred 

 to the genus Coelidium, 1 it has an open umbilicus extending to the tip of 

 the spire, but Coelidium, of which we have representatives in this fauna, 

 carries a slit band. A few of our many specimens suggest on the internal 

 cast but not on the exterior the presence of a slit band, very vague and 

 uncertain, confined to the later whorls only and though this evidence is 

 slender, not shown on the outside, it points to the relation of this shell to 

 Coelidium. So peculiar is the aspect of the shell that it may be well to 

 distinguish it by the generic term used above. 

 Horizon. No. 1 1. 



Platyceras sp. 



Plate i, figure 13 



A rather large deeply furrowed and corrugated shell similar to P . 

 retrorsum Hall of the Helderbergian [see Palaeontology of New York, 

 1859. 3: 320, pi. 58, fig. 10 ; pi. 59, fig. 9]. 



Horizon. No. 10. 



Euomphalus disjunctus Hall 



Plate 2, figures 10-14 



Euomphalus disjunctus Hall. Palaeontology of New York. 1859. 3: 340, pi. 



6 s; fig- 8 ; P 1 - 6 7, fig- 4 



This species was described from internal casts and the specific name 

 has reference to the condition of these whorls in the cast, but the speci- 

 mens from Dalhousie where the shell is abundant and shows nothing to 

 separate it from the New York form, retain the shell substance and show 

 clearly the union of the whorls throughout their course. In these too the 

 difference between the upper and lower sides of the spiral is well marked, 

 the former being but slightly overpassed by the final whorl while the latter 

 is deeply depressed. 



Horizon. No. u. 



1 N. Y. State Mus. Mem. 5, p. 67. 



