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NEW YORK STATE MUSEUM 



of 20 mm in the mature phragmocone and five in the same space 

 "in the apical portion of the shell. The sutures appear undulat- 

 ing; they are provided with a ventral saddle, whose hight is in 

 some measure proportional to the nearness of the siphuncle to 

 the wall of the phragmocone; this saddle is flanked by broad, low 

 lobes, which are followed by broad and higher lateral saddles, which 

 on the dorsal side inclose a short low lobe. The septa are mod- 

 erately convex, about one and a half times as deep as the cameras. 



The siphuncle is circular in section, large (two fifths th 

 width of the conch) ; subventran in position, but not in eontact 

 with the outer shell and distant from the latter by one fourth 

 of its diameter (5 mm when its width is 20 mm). In the apical 

 region it forms a nepionic bulb [pi. 5, fig. 1] having a length 

 of about 35 mm from the apex to the widest point and a maximum 

 width of 10.5 mm, protruding beyond the chambered shell in its 

 posterior part. A large portion of the siphuncle is filled with long 

 conical endosiphosheaths which leave open a fine endosiphotube 

 [see pi. 4, fig. 2]. In the cameras of the older parts of most larger 

 specimens organic deposits are found which frequently reach the 

 outer walls and completely fill the cameras [see pi. 6, fig. 1 ; pi. 9, 

 fig- I_ 3l- The surface is smooth. 



Position and localities. This species is very common in the dove- 

 colored limestone of Isle LaMotte (C x ) and Valcour island and in 

 the like beds exposed near Little Monty bay south of Chazy 

 village. It has also been observed in the lower Chazy of the Valcour 

 shore (123 B 4 ). 



Observations. The most striking character of this species is the 

 organic deposit in the chambers. Its character and appearance on 

 the septa and siphuncle vary greatly in the same individual, the 

 variation depending upon the distance from the living chamber. 

 The organic deposit is heaviest in the apical region of older indi- 

 viduals and diminishes in apertural direction. It appears to have 

 been formed, as a rule, slightly in advance of the filling of the 

 siphuncle by the endosiphosheaths and is hence absent in the greater 

 (anterior) part of the phragmocone. It also is frequently more 

 developed on the antisiphuncular side than on the opposite 

 one and appears to have been heavier and more developed in 

 the specimens of one locality than in those of another. 

 It is most strikingly developed in the specimens from the east side of 

 Valcour island and but weakly in those from Isle La Motte and 

 Little Monty bay and not at all in the specimens from the Lower 

 ( hazy of the Valcour main shore, referred to this species. 



