186 PALAEONTOLOGY OF NEW-YORK. 



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



Pl. XL. Figs. 1 a,bc,d. 



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

 rapidly enlarg-ing and abruptly expanded at the aperture ; aperture broadly semicircular 

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

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

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



This shell is not unlike Bellerophon cornuarietis ( Sowerby, Min. Conchology, tab. 469, 

 fig. 2 ) ; but tlie 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. 

 Tiie broadly expanded aperture and oljtuse carina of tlie last volution are prominent 

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

 sufficient to enalile ns to identify the species. The strongly marked carina commences at 

 tlie 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 margin, 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. 



{State Collection.) 



244. 4. BUCANIA BIDORSATA («. s;;.). 



Pl. XL. Fig.s. 8 o, 6, 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 abruj^tly expanding to- 

 wards tlie aperture ; dorsal margin witii 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 l)elweeii the centre and margin 

 of tlie shell ; surface ornamented by transverse fililorm striie, wliicli, receding from the 

 umbilicu.s, bend abruptly backwards near the centre, making a more gentle curve on the 

 dorsal band ; aperture sublunate. 



In young specimens, the carinal btiiid is very consjiicuous, willi a narrow elevated 

 central line. The lateral carinje or ridges scarcely all'ect tlie directijii of the stria> ; the 

 de])ressions on the outside of these ;ue less conspicuous lliaii on the inner side. In this 

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



