96 PALEOZOIC PALEONTOLOGY. 
Rensseleria subglobosa n. sp. 
Megambonia parva n. sp. 
Orthoceras sp. undet. 
Homalonatus vanuxemi Hall. 
?. Dalmanites dentatus Barrett. 
South of the last-described locality the trilobite bed has not been 
detected in situ, although some of the species of the fauna have been 
observed. The most characteristic species of the fauna, besides Dal- 
manites dentatus, are Rensseleria subglobosa and Chonostrophia jer- 
vensts, all three of these species having been originally described from 
this horizon in New Jersey, and being known nowhere else at pres- 
ent. The constitution of the fauna is peculiar and intersting, both 
Helderbergian and Oriskany species being associated in the same bed. 
Clarke* has considered these trilobite beds to be the upper portion 
of the Kingston beds, so placing them below the Helderberg-Oriskany 
boundary line. The presence in the fauna, however, of such char- 
acteristic Oriskany species as Orbiculoidea ampla, Stropheodonta mag- 
nifica, Anoplia nucleata, Spirifer murchisont and Cyrtina rostrata 
seems to indicate the Oriskany age of the fauna, although the asso- 
ciation with these species of a large number of Helderbergian forms 
emphasizes the low position of the fauna in the Oriskany. A careful 
study of the Helderberg and Oriskany faunas in New Jersey has 
brought out conspicuously the absence of any sharp dividing line 
between these two horizons, either of a stratigraphic or of a faunal 
nature. The faunal change in passing from the Coeymans limestone 
to the New Scotland beds is a much more pronounced one than that 
in passing from the Helderbergian to the Oriskany. This mingling 
of Helderberg with Oriskany species is not confined to the Dalmanites 
dentatus fauna alone, but is a noticeable feature, also, in the next 
succeeding zone. All of the Oriskany faunas in the Delaware valley 
region of New Jersey belong, essentially, to the calcareous facies of 
the formation, and are more or less closely allied to the Oriskany 
fauna of Becraft mountain, in New York, which has been so well 
described by Clarke.t The Dalmanites dentatus fauna of New Jer- 
sey, however, is believed to be somewhat older than Clarke’s Becraft 
mountain fauna, the latter corresponding more closely in age with 
the fauna of the Orbiculoidea jervensis zone in New Jersey. 
LR wR oe 
* Mem. N. Y. State Mus., No. 3, vol. III, p. 16. 
t Loc. cit. 
