ADDENDA. 
403 
notwithstanding it is so abundant at this locality, it is extremely rare at 
the distance of a few miles : indeed I have no specimen in my collection 
from any point five miles distant from the one here indicated. 
The Trematospira costata is so extremely rare, that but a single speci¬ 
men was obtained in all this time ; while among collections subsequently 
made by other parties, I have detected two other individuals. 
The Spirifer concinna is abundant in the Upper Pentamerus limestone 
(the rock succeeding the Shaly limestone), at Schoharie and Cobleskill; 
but I have seen only the single specimen from the shaly limestone, during 
all these years of collecting in the Helderberg. A similar example occurs 
in the little Rhynchonella semiplicata, which is abundant in the Pentamerus 
limestone, a heavy bedded stratum lying below the Shaly limestone ; 
while but two specimens have been seen in all these collections from the 
latter rock. 
It has not been in my power to make collections in other localities, 
with the same degree of care and completeness as from this one. 
Orthis oblata. 
“ discus. 
1843 
to 
1853. 
.. 2384 
1853 
to 
1857. 
277 
Since these determinations were made, I have separated 
from them the species O. discus ; but the proportional 
number of specimens has not beon ascertained. 
Orthis subcarinata_ 
“ planoconvexa.. 
Orthis perelegans_ 
.. 2783 
.. 456 
458 
158 
A later critical examination of the specimens referred to 
the Orthis subcarinata, has enabled me to separate 
from all the collections ten specimens of O. plano¬ 
convexa. 
“ tubulo striata _ _ 
14 
21 
“ deformis.. 
1 
1 
“ eminens. 
0 
0 
This species is extremely rare in the Ilpldcrberg moun¬ 
tains. 
“ variea.. 
..40000 
3960 
The falling off in the product of this species arose from 
the little encouragement given to collect the specimens, 
and perhaps from partial exhaustion. 
Orthis (small) _ _. 
.. 500 
353 
These specimens are, perhaps, the extreme young of 0. 
oblata and allied species. 
Cl u 
.. 150 
229 
These specimens are probably the extremely young in- 
Orthis strophomenoides 
.. 12 
dividualsof 0. subcarinata and O. perelegans, which 
are not easily distinguishable from each other. 
Strophomena depressa 
.. 50 
20 
Trematospira costata.. 
“ multistriata. 
1 
.. 15 
0 
0 
Two other specimens of this species have since been ob¬ 
tained by other parties, making three now known. 
