PALEONTOLOGY, 99 



different specimens, and changes during the progress of growth. A 

 specimen may begin with a narrow cylindrical base, and then sud- 

 denly spread its end cell into an expanded dish form, or another 

 may very regularly and gradually dilate into curved, horn-shaped 

 cells, or the conical calyces of the base, after attaining a certain 

 diameter, may stop to dilate and continue to grow on, maintain- 

 ing the same size, into long, cylindrical stems, straight, or curved, 

 or geniculated by interruptions in the growth, with constrictions 

 and deflexions. In regularly formed specimens the calyces are 

 shallow, bell-shaped, with broadly spread margins ; other speci- 

 mens have deeper calyces, with nearly erect margins. The radial 

 lamellae are alternately shorter and longer, but equal in size near 

 the calyx margins, forming a uniform, uninterrupted cycle, with ex- 

 ception always of a faintly indicated apertural gap and septal 

 fovea. The longer lamellae extend as somewhat flexuose crests to 

 the centre. Often a lamella continues across the calyx from the 

 centre of the apertural gap to the opposite side, and the other 

 lamellae abut against it from both sides in symmetrical order. The 

 bottoms of the end cells are usually raised into obtusely rounded 

 monticulose protrusions, on which the lamellae unite with interlaced!,, 

 twisted ends ; or sometimes the lamellar crests fade away befQire- 

 reaching the centre, which then is formed by a smooth, naked spQfc 

 of narrow extent. The most obvious character of this species are- 

 the arched carinas extending across the lateral faces of the lamellae 

 from the outer peripheral side and below, to the upper and inner 

 edges of the lamellae ; the carinations correspond on both- faces, 

 and project on the edges of the lamellae as obtuse, transverse bars; 

 or as acute dentations. The carinas of different specimens vary 

 considerably in degree of approximation ; in some about eight 

 carinae are in the space of one centimeter, while others may have 

 as many as fifteen within the same space. The radiallamellae are 

 acute, linear, and the interstices between them are completely filled 

 by vesiculose, transverse plates arranged in imbricated superposi- 

 tion, in arched rows, ascending from within and below, upward and 

 outward, diagonally to the direction of the carinae. In the central 

 area the polyparia are intersected by diaphragmatic, transverse 

 plates, usually compound, of several pieces, inclosing larger vesicu- 

 lose, interstitial cavities, which, by intersection with the vertical 

 lamellae, are divided into cellulose spaces of a much coarser kind 



