Raymond : Gastropoda of the Chazy Formation. 207 



of which increases with the expansion of the shell. Aperture large, 

 nearly circular. The section of the body whorl has its upper side 

 nearly straight, meeting the straight outer side at an obtuse angle. The 

 inner and lower sides of the section are rounded. The umbilicus is 

 very small. 



All the specimens in the collection are casts of the interior and do 

 not show anything more than traces of the surface markings. 



Locality. — A rare species from the Chazy at Valcour Island, New 

 York. 



The type is in the collection of the Carnegie Museum. 



Trochonema hudsoni Raymond. 



(Plate LIV, figures 1-3. ) 



Holopea hudsoni Raymond, 1905, American Journal of Science, Series 



4, Vol. XX, p. 378. 



Specimens of this species are usually casts of the interior and in that 

 condition they show the smooth rounded whorls of a Holopea, under 

 which genus they were originally described. Certain revolving lines on 

 one of the casts caused Dr. Ulrich to suspect that the shell might be a 

 Trochonema of the same type as the Trochonema obsoletum described 

 by him from the Trenton of Kentucky. Further search in my collec- 

 tion brought to light a fragment of the body whorl of a testiferous 

 specimen which shows distinctly the flattened peripheral band. The 

 description must therefore be considerably revised. 



Description. 



Shell Holopea-like, with rounded volutions. There are usually four 

 whorls, the body whorl being about three times the height of the spire. 

 A testiferous example shows a wide, flattened peripheral band, above 

 which the whorl is somewhat flattened, and directly above the carina 

 almost concave. Below the band the shell is gently convex. In the 

 cast some specimens show a very slight flattening of the upper side, 

 while in other specimens the cast of the body whorl is regularly rounded, 

 with two or three faint revolving ridges below the center of the whorl. 

 In the casts the whorls of the spire are regularly rounded, and the 

 suture is very deep. The spire of the specimen retaining the shell is 

 broken away. The umbilicus is small, almost closed by the thicken- 

 ing of the inner lip. The aperture is almost circular in outline and 

 the inner lip is free from the body whorl except in the posterior inner 



