186 PALJEONTOLOGT OF NEW-OTORK. • , " 



*■ 



243. 3. BUCANIA EXPANSA ( n. sp.). 



Pu XL. Figs. 1 a, b c, d. 



Convolute, trumpet-shaped ; volutions three or four, subangular, the last one elongated, 

 rapidly enlarging and abruptly expanded at the aperture ; aperture broadly semicircular 

 or sublimate, with a sinus at the dorsal side ; dorsal line obtusely carinated ; section of the 

 last volution, below the aperture, subtriangular ; of the inner volutions, subelliptical, with 

 the extremities obtusely angular ; original surface striated. Specimen a cast. 



This shell is not unlike Belleropkon comuarietis (Sowerby, Min. Conchology, tab. 469, 

 fig. 2); but the volutions in that species are represented as not contiguous. The species 

 under consideration differs from either of the two preceding in a very obvious manner. 

 The broadly expanded aperture and obtuse carina of the last volution are prominent 

 features ; and in fragments, the subtriangular form of sections of the last volution are often 

 sufficient to enable us to identify the species. The strongly marked carina commences at 

 the base of the last volution, and continues to the aperture. The volutions are closely 

 pressed against each other, the convex dorsal side producing a corresponding depression on 

 the ventral side of the contiguous volution. 



Fig. 7 a.- View of the back of the shell, showing the strong carina, expanded aperture, and sinus on the 

 dorsal margiiL b. Lateral view of the same. 



Fig. 7 c. Transverse section of the last volution, below the aperture. 



Fig- 7 d, e. Lateral and front view of another specimen, from which the expanded portion of the aper- 

 ture is broken off, and showing also a little deviation in form. 



Position and locality. In the lower irregularly bedded portions of the Trenton limestone, 

 and in the strata resting on the Black-river limestone, at Watertown, Jefferson county. 



(Statt Collection.) 



244. 4. BUCANIA BIDORSATA (n.5j9.). 



Pi.. XL. Figs. 8 a, b, c, d, e,f, g. 



Convolute, subglobose, with a deep umbilicus ; volutions about three, the last one 

 extended and somewhat straight, gradually enlarging and more abruptly expanding to- 

 wards the aperture ; dorsal margin with a double or grooved carina, on the centre of which 

 is a narrow elevated line ; on each side of the dorsal band is a broad groove or depression, 

 and an obtusely angular ridge, the latter being half way between the centre and margin 

 of the shell ; surface ornamented by transverse filiform striae, which, receding from the 

 umbilicus, bend abruptly backwards near the «en(re, making n more gentle curve on the 

 dorsal band ; aperture sublunate. 



In young specimens, the carinal band is very conspicuotis, with a narrow elevated 

 central line. The lateral carinas or ridges scarcely affect the direction of the striae ; the 

 depressions on the outside of these are less conspicuous than on the inner side. In this 

 respect, however, there is some variation in specimens from different localities. In casts of 



