ADDENDA. J 93 



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. 



1843 18S3 



lo lo 



1893. 1»57. 



rirtliia nKlafa 9'XiiA 977 Since these determinations were made, I have separated 



uriiiis ooiaid ^ooi a i i j.^^^ ^^^^^ ^^^ species O. discus ; but the proportional 



'' flisrilS number of specimens has not Ijeen ascertained. 



Ortllis SUbcBrinata 2783 458 A later critical examination of the specimens referred to 



the Orthis subcarinata, has enabled me to separate 

 " plflnOCOIlVCXcl from all the collections ten specimens of O, plano- 



' - - . • conveza. 



Orthis perelegans 456 158 



" tubulostriata 14 21 



" deformis 1 1 



u cniincns This species is extremely rare in the Helderberg moun- 



"'"" tains. 



" Varica 40000 3960 "^^^ failing off in the product of this species arose from 



' •■■" the little encouragement given to collect the specimens, 



and perhaps from partial exhaustion. 



Orthis fsmain 500 353 These specimens are, perhaps, the extreme young of O. 



^ J-------'-- oblata and allied species. 



(1 u 150 229 These specimens are probably the extremely young in- 



"" "" dividuals of O. subcarinata and O. perelegans, which 



are not easily distinguishable from each other. 



Orthis strophomenoides . . 12 

 Strophoraena depressa .. 50 20 



Tromnt/^anii.o nrtatata 1 fl Two other specimens of this species have since been ob- 



irematOSpira COSiaia l W taincd by other parties, making three now known. 



" multistriata 15 



