WAVEELY GROUP SPECIES. 311 



physiognomy, it differs from the t^^pical species of AUorisma, and hence 

 it may be thought desirable to establish a subgenus for its reception, in 

 which case I have elsewhere proposed for the group the name Cercomy- 

 opsis 



Along with the typical specimen of the foregoing species another was 

 found, with the same form and surface characters, excepting that its 

 anterior end, in front of the beaks, is shorter, and more angular at the 

 lower end of the lunule, while the anterior of its radiating costse are 

 directed much more obliquely backward, instead of descending nearly 

 vertically from the beaks to the base. This specimen (see fig. 4&) has 

 the posterior end broken away, but as the peculiarities mentioned seem 

 not due to any distortion, it may possibly belong to another species ; if 

 so, AUorisma {Sedgwickia ?) obliqua would be a good name for it. 



Locality and position ; Rushville, Oliio. Waverly group of Lower Carboniferous. 

 Prof. Andrews's collection. 



x\llorisma Winchelli, Meek. 



Plate 16, figs. 3a, h, c. 

 AUorisma Winchdli, Meek (1871), Proceed. Acad. Nat. Sci., Philad., XXIII, 167. 



Shell of about medium size, elongate subelliptic, the length being equal 

 to about three and a half times the height, moderately convex; posterior 

 extremity a little gaping, obliquely subtruncated above and narrowly 

 rounded below the middle ; anterior extremity very short, closed, concave 

 in outline obliquely forward and downward from the beaks above to the 

 lower end of the lunule, where it is subangular, and from this point 

 rounding off obliquely into the base; ventral margin forming a broad, 

 gentle curve, but generally somewhat straightened, or sometimes faintly 

 sinuous near the middle ; dorsal margin nearly straight, or a little con- 

 cave in outline, and showing the usual inflection, which forms a lanceo- 

 late escutcheon with a slight ridge on each side, from the beaks to the 

 posterior extremity of the hinge, which equals about three-fourths the 

 entire length of the valves; beaks much depressed, very oblique, in- 

 curved, and located only about one-fourteenth the entire length of the 

 shell from the anterior extremity; posterior umbonal slopes merely some- 

 what prominently rounded; anterior umbonal slopes generally slightly 

 subangular near the beaks, and sometimes this prominence is obscurely 

 continued as a faint rounded ridge obliquely backward and downward 

 to a point a little in advance of the middle of the base. Surface orna- 

 mented with concentric lines and ridges of growth, that generally assume 

 the character of little regular wrinkles on the umbones. Lunule small, 

 rather deep, moderately well defined, and obovate in form. 



