I04 NEW YORK STATE MUSEUM 



mens in the Snake Hill shale. These exhibit the characteristic 

 sculpture of the species, consisting of relatively distant pits placed in 

 radiating grooves. The largest specimens, attaining a length and 

 width of about 8 mm, agree in outline with the typical material from 

 Clifton, Tenn., while the smaller individuals are narrower and with 

 more prominent beaks, suggesting in this regard the later T. u m - 

 b o n a t a Ulrich. Considering this difference and that in size, it 

 is seen that the Snake Hill form, may properly be considered as a 

 smaller variety. It is evident that the whole Snake Hill fauna is 

 largely a microfauna due to the unfavorable shale facies, and that 

 one could recognize a considerable number of forms as small 

 varieties of species occurring in larger individuals in the limestone 

 facies of the Trenton. 



Trematis punctostriata was originally described 

 by Hall in the 23d Report, New York State Cabinet of Natural His- 

 tory, 1873, ^^d has been fully figured by Hall and Clarke in the 

 Palaeontology of New York, volume VHI, plate IVG. It has more 

 recently been discussed by Foerste (1910, p. 37) who describes the 

 shell as large, attaining a width of 30 mm; being nearly circular in 

 outline; the width a little greater than the length. The brachial 

 valve is, in our specimens as in the typical material, " moderately 

 convex, the convexity increasing toward the beak." The radiating 

 rows of pits are closer together, and the pits larger, in the anterior 

 half of the shell, according to Foerste, eight to eleven rows occupy- 

 ing a width of 2 millimeters. We have counted eleven rows, on frag- 

 ments, of the anterior portion, within the mentioned space. " Poste- 

 riorly, especially along the umbonal part of the shell, the radiating 

 rows are more distant, and appear like narrow grooves crossing an 

 otherwise comparatively flat surface." These grooves near the edges 

 of the posterior portion are well seen in the figures here given of the 

 variety minor, 



3 Trematis terminalis (Emmons) 



Another Trematis of the Snake Hill shale, north of Albany, 

 deserving mention in this place, is T. terminalis Emmons. 

 This form, formerly known only from the Trenton limestone in New 

 York (Middleville, Trenton Falls, Watertown etc.) occurs in large 

 individuals, attaining a length and width of 12 mm. 



4Triplecia nucleus (Hall) 

 We refer a small Triplecia from the Snake Hill shale at North 

 Albany to this species because of its subcircular outline, small size of 



