Lower and Middle Taconic. — Marcou. 365 
teenth Ann. Eep. State Cabinet Nat. Hist, of New York, 
Albany, March, 1861), which at p. 116, under the name Barran- 
dia thompsoni, gives a figure,' most inexact in many important 
genetic points, of the already celebrated Georgia trilobite. The 
head, thorax, and more especially the pygidium figured and 
described by Mr. Hall are very defective and misleading. So 
it is not astonishing that professor Broegger made the mistake 
of referring the Scandinavian trilobite of Nathorst, Linnarsson 
andKjerulfto Olenellus {Elliptocephalus). 
As far back as 1862, in one of my numerous visits to Geor- 
gia, I found a complete specimen of the so-called Olenus, 
Barrandia and Olenellus thompsoni^ but by some mischance 
my specimen was not figured and described until February, 
1884, by Mr. R. P. Whitfield in the Bulletin Amer. Museum 
Nat. Hist. vol. i. No. 5, plate xv, fig. 1, and p. 151, New York. 
Mr. Whitfield corrected the description and figure of Mr. Hall 
to such an extent as to make almost not only a new species, 
but also a new genus. The remarkable length of the pygidium, 
or rather caudal spine, as he says, is "a generic distinction." 
If professor Broegger had seen that figure and description of 
Mr. Whitfield, he would not have referred his Scandinavian 
trilobite to Olenellus. It was reserved to Dr. Gerhard Holm, 
to give in 1887, a most elaborate and truly reliable description 
and figure of the Scandinavian type of that contested trilobite, 
first placed in Paradoxides and afterward in Olenellus. In 
his paper "Om Olenellus kjerulUr Dr. Holm shows generic 
distinctions; more especially for the pygidium, which is as 
nearly as possible a Paradoxides pygidium, and completely 
different from the spare-like or telson pygidium of Olenellus; 
also thoracic differences ; and finally the "growing together 
of the cheeks with the middle part of the head and the peculiar 
elongation of the suture." A study of Dr. Holm's excellent 
figures and description lead forcibly to the opinion that 
Olenellus hjerulii is not an Olenellus {Elliptocephalus) at 
all, but a new genus intermediate between Paradoxides and 
Elliptocephalus, more closely related to Paradoxides, its 
most immediate successor in chronological order, on account 
of the pygidium ; and I fully concur with Mr. G. F. IMatthew 
who had proposed to use the name of Dr. Holm for the new 
'The fii^ure was drawn from more or less fragmentary ppecimcns. 
