"Ism*"'] PROCEEDINGS OF THE NATIONAL MUSEUM. 39 



Helenia gen. nov. 



Shell an elongate, narrow, flattened, curved tube ; transverse section 

 and aperture elliptical. Surface marked by transverse, concentric, im- 

 bricating lines of growth. 



Helenia bella sp. nov. 



Shell an elongate, narrow, flattened, curved tube. The plane of the 

 flattened surfaces is slightly twisted, so as to throw the lateral margins 

 about one-quarter of a turn around and to incline the upper and lower 

 faces nearly 45° at one extremity, as compared with the other. The 

 curvature is nearly semicircular. The cross-section is an elongated 

 ellipse. The form of the aperture of the larger extremity, as indicated 

 by the striae of growth, has the peristome arching forward on one of 

 the flattened sides and curving slightly backward on the opposite side. 

 As far as I am able to determine the shell was open at the smaller end, 

 as in Dentalium, or the extremity was decollated in all the specimens 

 collected. I am inclined to think that it was open at both ends, and 

 hence should be referred to the Dentalidcv. 



Surface marked by irregular, transverse or concentric, imbricating 

 lines of growth that vary in number and size on the same specimen 

 and in different specimens. 



Helenia bella is provisionally referred to the Dentalidce on account of 

 its form ami the apparent opening at both extremities. 



Formation and locality. — In a pinkish-colored limestone of Lower 

 Cambrian age, in association with Hyolithes princeps, Olenellus broggeri, 

 etc. In a railway cut north of Manuel's Brook, Conception Bay, New- 

 foundland. 



Nat, Mus. Cat. Invt. Foss., No. 18324. 



Agnostus desideratus sp. nov. 



Cephalic shield about as broad as long, broadly rounded in front, sides 

 curving in very slightly towards the posterior margin ; posterior margin 

 sloping obliquely inward from the postero lateral angles to the median 

 lobe. A narrow raised rim extends all around the margin except across 

 the base of the glabella or median lobe. The space between the rim 

 and the glabella is slightly convex. Glabella less than two thirds the 

 length of the head, narrow, subcylindrical, and with a small tubercle 

 on the posterior third. Surface smooth. A pygidium associated with 

 the head on the same piece of rock has a prominent median lobe bor- 

 dered by a narrow convex space between it and the marginal rim. The 

 median lobe does not show auy indication of lateral or transverse fur- 

 rows. An elongate median tubercle is the only ornament. 



This type of Agnostus occurs in the Middle Cambrian zone of the 

 Atlantic Basin as A. parvifrons, Liunarssou, and A. brevifrons, Linnars- 

 son, of Sweden, and A. tessella, Matthew, and A. umbo, Matthew, of New 

 Brunswick. 



