NOTICE OF PALEONTOLOGY OF NEW-YORK, VOLUME IV. 1 47 



In the Portage and Chemung groups, we have 



Orthis cariiiata, 

 O. tioga (n. s.), 

 O. i?npressa, 



O. 

 O. 

 O. 



leonensis (n. s.), 

 thiemei, and 

 leucnsia ? 



Under the Genus Streptorhynchus, several species heretofore described 

 are referred to Strophomena ( Streptorhynchus ) chemungensis, Conrad, 

 under which, as varieties, are arranged Strophomena bifurcata, S. arcto- 

 striata, S. pectinacea, and Orthis perversa (Hall) ; Streptorhynchus pan- 

 dora (Billings) ; Orthisina arctostriata and O. alternata (Hall) ; Orthis 

 inequalis and O. pravus (Hall, Iowa Report). The species is extremely 

 variable, having a great vertical and horizontal distribution, and appears 

 under many phases. 



The Strophomena rhomboidalis (Wahlenberg ) = S. rugosa ( Rafi- 

 nesque) occurs in the Schoharie grit, and is abundant in the Corniferous 

 limestone, but is unknown in the Hamilton and Chemung groups. 



The Genus Strophodonta extends throughout the series ; and two 

 species, the S. demissa and S. perplana^ are found from the Schoharie grit 

 to the Chemung group inclusive. The species recognized in the Upper Hel- 

 derberg group are : 



Strophodonta demissa ^ 

 S. perplana^ 

 S. alveatay 



S. 

 S. 



s. 



inequiradiatay 



patersoni, 



he?nispherica, 



S. callosa, 



s. 



inequistriatay 



S. parvay 



S. orehristriatay 



s. 



ampla . 



In the Hamilton group are found : 



Strophodonta concava, 



S. perplanay Conrad (which has been described under the names 

 Strophomena perplana^ S. pluristriata, and S. delthyris, Con- 

 rad ; and as S. iiervosay S. crenistria, and S. fragilis, Hall); 



S. 



demissay 

 nacreay 



In the Chemung group are found 



Strophodonta cayuta (n. s.), 

 iS. mucronatay 



S. coslata (n. s.)j 



S. inequistriata, 

 S. junia. 



S. perplana var. nervosay 

 S. demissa. 



In the Genus Chonetes, we find verified in a very satisfactory manner 

 the observations made by Count Von Keyserling, in regard to the direc- 

 tion of the tubes or spine-bases in the area of the ventral valve. These 

 tubes are directed from the hinge-line towards the apex of the valve, and 



