74 



NEW YORK STATE MUSEUM 



APARCHITES Jones 



Aparchites minutissimus Hall var. robustns var. nov. 



Leperditia (I s o c h i 1 i n a) minutissima Hall. De- 

 scrip, sp. foss. Hud. riv. gr. 1871. p. 7 



PI. 7, fig. 6-11 



In the black compact limestone associated with R e m opleu- 

 rides linguatus several specimens of Aparchites were 

 found, which not agreeing fully with the description of the 

 species above cited are considered as representing a variety of it. 



Diagnosis. Carapace elongate oval, rather large for this genus, 

 cardinal margin slightly concave, cardinal angles rounded, 

 anterior margin narrowly rounded, ventral margin obtuse pos- 

 teriorly, posterior margin broadly and evenly rounded, postero- 

 dorsal part truncate. Valve quite strongly and very evenly con- 

 vex, highest part near the center, or a little posteriorly and ven- 

 trally of the center. Ventral edge narrowly and slightly beveled. 

 No sulcus, eye tubercles, or muscle impressions observable. Sur- 

 face smooth. 



Dimensions. Largest specimen (fig. 9): length, 2.4 mm; hight, 

 1.4 mm; thickness .7 mm. 



Horizon and locality. Black compact limestone pebbles of the 

 Rysedorph hill conglomerate. (Group 5) 



Observations. Two specimens have been figured, which present 

 considerable difference in relative hight and length, the larger, 

 which is about normal, being relatively longer than the smaller 

 and relatively higher specimen. This type does not present any 

 marked differences from Aparchites minutissimus, 

 specially from the Trenton variety of this species, described by 

 Ulrich, except in the great difference in size, this form being 

 more than twice as large as the other. 



