KLOEDENELLIDAE 



55 



A^enter curved ; anterior end thickest but nar- 

 rower than posterior; sulcus postcentral, 

 traversed by short, thin rib or carina in- 

 clined toward venter, anteriorly merging 

 with thickening of valve at this point, 

 terminating abruptly just back of sulcus; 

 valves irregularly inflated anteriorly, less so 

 between sulcus and venter, producing shal- 

 low saddle-like area in antero-ventral quar- 

 ter; edges near free margins abruptly up- 

 turned in false keel or basal portion of frill, 

 which has been broken completely from 

 this specimen. 



Length, 0.82 mm; height, 0.46 mm; 

 thickness, 0.31 mm. 



Golconda formation, locality 22, rare. 



Denisonia cirrata Cooper, n. sp. 



Plate 11, figure 34 



Carapace elongate, posterior swing pro- 

 nounced ; dorsal line straight, ends rounded, 

 venter curved ; greatest height postcentral ; 

 valve uniformly inflated around deep sulcus 

 located postdorsally of center ; sulcus tra- 

 versed by short, triangular platform-like rib 

 rising almost perpendicular from surface; 

 rib widest anteriorly, merging with surface 

 of shell behind sulcus ; hingement cardine ; 

 frill composed of elongate, needle-like spines 

 in row which parallels free margins. 



Length, 0.71 mm; height, 0.38 mm. 



Golconda formation, locality 18, rare. 



This species is distinguished by its pro- 

 minent backward swing and by its short and 

 unusually wide carina. 



Genus Geffenina Coryell and Sohn 



Geffenina? praelonga Cooper, n. sp. 



Plate 11, figures 42-44 



Carapace large, elongate, ends rounded ; 

 dorsal margin straight, venter broadly 

 curved; overlap around entire free margin, 

 very prominent, especially on anterior end ; 

 hinge straight, slightly more than half 

 length of shell, slightly depressed and 

 notched at ends; greatest thickness and 

 height in anterior quarter; greatest length 

 central; median sulcus deepest midway be- 

 tween dorsum and venter, becoming shal- 

 lower upward; posterior sinus indistinct, 

 resulting in poorly-defined lobe. 



Length, 0.95 mm; height, 0.58 mm; 

 thickness, 0.51 mm. 



Golconda formation, locality 19, com- 

 mon. 



Genus Jonesina Ulrich and Bassler, 

 emend. Cooper 



Jonesina, in the original description, was 

 included in the family Beyrichiidae, sub- 

 family Kloedenellinae, the latter being sub- 

 sequently raised to family rank. In their 

 remarks on the Kloedenellinae Ulrich and 

 Bassler (1908, p. 320) describe the "valves 

 as more or less distinctly overlapping. As 

 a rule, the overlap is confined to the ventral 

 side and ends." The genotype by original 

 designation is Beyrichia fastigiata Jones and 

 Kirkby from Carboniferous (Mississippian) 

 beds of Scotland. Unfortunately, one of the 

 figures reproduced by Ulrich and Bassler to 

 illustrate the genotype shows an overlap 

 along the dorsal margin. Neither Jones and 

 Kirkby nor Ulrich and Bassler give ade- 

 quate description of the hingement. Kellett 

 (1933, p. 76) explains the dorsal overlap in 

 this figure as the ''thickened edge of the 

 left valve showing around the cast of the 

 right." Bassler and Kellett's (1934) de- 

 scription of Jonesina fits several genera of 

 Kloedenellidae equally well, for instance 

 Sansabella. Roundy describes the hinge of 

 Sansabella as "straight, equal in both valves 

 and, in part, slightly lower than the dorsal 

 margins of the two valves, giving an ex- 

 cavated or channeled appearance in the 

 dorsal view of a bivalved specimen." In ad- 

 dition to the channel the Sansabella hinge 

 contains a delta-shaped notch at each end 

 of the hinge line, the apical point of the 

 delta pointing to and overlapping the 

 smaller valve. These features, namely the 

 straight hinge line, V-shaped in cross-section, 

 and termination at each end by a triangular 

 notch constitute the sansabelloid hingement 

 of many descriptions, not only of Sansa- 

 bella, but of a number of subsequently de- 

 cribed genera. 



Kellett (1933, p. 77) thinks it "would be 

 well to place in the genus Sansabella only 

 those species which are known to have the 

 well developed denticulation as decribed 

 by Roundy." By the same token it might be 

 said that all species with the sansabelloid 

 hinge should belong in Roundy's genus. 



