98 NEW YORK STATE MUSEUM 



as occurring in '' the central and higher portions of the Trenton 

 limestone at Middleville, and in the calcareous layers in the Utica 

 slate at Coldspring, Montgomery county, N. Y." It has been 

 found by us to be not uncommon in the Canajoharie t>eds at Cana- 

 joharie and the old locality of Coldspring is in the same formation 

 not far away on the other (north) side of the Mohawk river. 



In the Geology of Minnesota (title 38, page 532), Doctor Ulrich 

 states of this species that it is almost certain that it belongs to his 

 genus Prolobella which he places with the Modiolopsidae, and that 

 it does not belong to the true Aviculidae, " their valves being equal 

 and without the prolonged posterior wing." 



Whitella elongata nov. 

 PL 5, fig. 9, 10 



Description. Shell of medium size, compressed, subrhomboidal, 

 a little wider posteriorly (by about one-fifth), length about 

 three-fifths greater than posterior width, and shell about six times 

 as long as thick. Anterior margin straight or even slightly concave 

 in upper part, probably subangular at the anterior extremity of the 

 hinge (the extremity not preserved) ; evenly rounded below, post- 

 basal angle not well seen, apparently also strongly rounded, posterior 

 margin very gently convex or gently straight (but partly seen) 

 gradually merging into the dorsal line. Beaks small and little promi- 

 nent and probably but little incurved, situated about one-fourth the 

 length of the shell behind the anterior extremity; umbonal ridge 

 very sharp at the beginning, possibly through oblique compression of 

 the shell, becoming obsolete before reaching the postbasal margin. 

 Surface gently convex posteriorly to the ridge and rather flat in 

 front and below it. Surface marked by coarser, distant lines of 

 growth and fine intercalated concentric lines. Escutcheon and 

 hinge not seen, muscular scars but faintly. 



Position and locality. Olive gray shaly sandstone of Snake Hill 

 (Trenton) beds at Snake hill, Saratoga county, N. Y. 



Doctor Ulrich writes me regarding this species that it belongs 

 in the group of W . c o m p r e s s a Ulrich and W . o h i o - 

 e n s i s Ulrich, but is more elongate. The former species occurs 

 in the Middle Third of the Trenton shales of Minnesota, the latter 

 in the lower Richmond beds of Ohio. We have obtained but a 

 single specimen of this species, which is obviously rare in our 

 Trenton shales. 



