88 COKKELATION OF GEOLOGICAL FAUNAS. [bull. 210. 
were selected and recorded, the imperfect ones being left and not 
mentioned in the catalogues. Nevertheless, the statistics give a slight 
indication of the prominent associates of Spirifer disjunctus. Among 
the prominent members of the dominant list of the species of the fauna 
it is safe to say that the following species frequently appear, viz: 
Table XXIIb. — Conspicuous species of the Spirifer disjunctus fauna. 
Spirifer disjunctus. 
Camarotcechia contracta. 
Productella — some one of the forms of the lachrymosa or hirsuta forms and 
markings. 
Orthothetes chemungensis. 
Athyris angelica. 
Among the spirifers the typical Spirifer (Delthyris) mesicostalis with 
coarse plications and distinct septum does not appear in the Ithaca 
zone, but is common in the Upper Chemung zone. Spirifer mesi- 
st rial is is common in the lower Ithaca zone; and in the zone domi- 
nated by the Spirifer disjunctus fauna it is represented by Spirifer 
(Cyrtia) alia or Spirifer marcyi var., but is rarely associated with a 
pure Spirifer disjunctus t'aunule. 
The common Ithaca spirifer is S. pennatus var. posterns. It is often 
called ' 'mesicostalis ," but generally has finer plications and is always 
without distinct septum in the Ithaca zone, thus separating it from 
Delthyris mesicostalis of the typical Spirifer disjunctus fauna. 
The rhynchonellas (Camarotozchia) show a definite succession of 
species. The Ithaca zone carries C. eximia and stephani, and occa- 
sionally forms identified as ( '. contracta; but typical ( '. contracla, with 
the small number of plications, is confined to the higher horizon, and 
runs into the forms called C. orbicularis and C. sappho or C. alle- 
ghenia in the typical higher Chemung. R. (Pugnax) pugn us is not 
found associated with the Spirifer disjunctus fauna, but is a species 
of the lower Ithaca zone. 
Among the productellas the forms called P. lachrymosa and its 
varieties do not appear in the fan miles till the disjunctus stage is 
reached. They are distinguished by their coarse, large, evenly 
rounded gibbous form. Although these are associated with the finely 
hirsute forms and others marked on the surface like P. speciosa, the 
form which is generally identified as P. speciosa is an earlier form. 
The Ithaca form is characteristically Productella speciosa, though 
showing some variation; the small rounded spine bases not drawn out 
so as to be oblong, and the low and pinched or narrow beak, with more 
or less rounded cardinal angles, are conspicuous distinguishing 
features. 
Although the original specimens named P. speciosa appear to have 
come from the western part of the State and a locality holding a typi- 
