BRACHIOPODA. 
309 
teeth are moderately developed, and indicate considerable divergence in the 
dental ridges. A most remarkable feature on these casts, is the presence, on 
each side of the umbo, of a minute, greatly elongate and gently tapering cone, 
the base of which is joined to the cast at about two-thirds the distance from 
the apex to the cardinal angle; and from this point each one is inclined toward 
the apex of the shell, and terminates in a free extremity. These delicate 
cones which are so fragile that they are easily lost and rarely preserved, 
penetrate, but do not transect the cavity originally filled by the substance of 
the cardinal portion of the valves; they are evidently the casts of a single pair 
of large and very oblique spine-tubes, which were not continued into spines as 
in Chonetes, and evidently did not penetrate to the outer surface of the cardi¬ 
nal margin. The inner opening of these blind tubes is situated below and in front 
of the cardinal area, and their obliquity greatly exceeds that observed in the cardi¬ 
nal tubes of Chonetes. The muscular impressions consist of two flabellate diduc- 
tors, between which lie two elongate, narrow adductors. Over the pallial region 
the surface is pustulose. In the brachial valve the cardinal process appears to 
be simply bilobate, the crural plates narrow and obscure. From the base of the 
cardinal process extend two slightly divergent median ridges which are con¬ 
siderably elevated at the center of the shell and terminate abruptly. These 
enclose an elongate muscular scar. There are also two lateral ridges curving 
outward and then inward, enclosing small thickened areas which appear to be 
of muscular origin, while the ridges themselves have the curvature of, and 
suggest the “ reniform impressions.” Nearly the entire inner surface of this 
valve is covered with radiating rows of strong pustules. This curious shell 
represents a phase of development in the chonetid type not hitherto described 
and it may be convenient to separate it under the sub-generic name Anoplia.* 
Illustrations of the only species known to possess these features, Leptma ? 
nucleata , will be found on Plate XVa, figures 17 and 18, and Plate XX, figures 
14-17. 
* Meek and Worthen, in describing this species under the name Leptcena? nucleata (Palaeontology of 
Illinois, vol. iii, p. 394 ; 1868), observed that “ this curious little shell does not present the form or internal 
characters of Lept^na, and will probably be found to be a new generic type.” 
