100 
PALEONTOLOGY OF NEW YORK. 
more naturally rest in association with Seminula suhtilita than with the group 
of Spirigerella Derbyi. 
We have no satisfactory evidence of the occurrence of Spirigerella in 
North American faunas. 
The type of structure characterizing Athyris is continued beyond the 
Palmozoic, being abundantly represented in the Alpine Trias faunas. These 
later fossils have been studied by various authors, and most recently de¬ 
scribed by Bittner,* who has subdivided them into a number of groups all of 
which he holds subordinate in generic value to Spirigera ( = Athyris). Of 
these, two principal divisions are made; 
(I) Forms with simple spirals; 
(II) Forms with double spiral bands. 
Of the former are : 
1. The “genuine Spirigeras”; under which are included ; 
a. Smooth forms. 
b. Species with sloping shoulders, retzioid rather than athyroid in out¬ 
line, and bearing on the surface a few sharp plications, which, at 
the margin, are opposite, not alternate ; Plicigera. 
Fig. 74. TetractineXla trigonella, Schlotheim. 
Fig. 75. Loop of Dioristella indistincta, Beyricl). 
Fig. 76. Amphitomdla kemispkaroidica, Klipstein. 
(UlTTNEK.) 
*Brachiopoden der Alpinen Trias: Abhandl. der k. k. geolc>g. Reichsanst., Bnd. xiv. 1890. 
