Se at ae Sh an otal ee ee ae —— 
ae oe 
BIBLIOGRAPHY OF PALALOZOIC . CRUSTACEA 9 
BEECHER (Charles E.)—Continued 
This form is similar to the preceding though larger, and with the glabella more 
rapidly expanding in front. ‘Ihe neck segment is the only one which is distinct. 
Ptychoparia linnarssoni Walcott, after Matthew. 
‘The axis is narrow, expanding in front, and obscurely ringed; 5 annulations be- 
longing to the head and one to the pygidium, which is very short and separated from 
the cephalon by a distinct groove. 
Ptychoparia kingi Meek. 
The author remarks that fig. 6 which is referred to a later stage, shows the incep- 
tion of several characters that have not as yet appeared in the previous larvae. ‘The 
axis is very strongly annulated; the anterior lobe is nearly as long as the 4 posterior 
annulations of the cephalon, and on each side there is a furrow representing the eye 
line of the adult; the free cheeks are present as narrow marginal plates including the 
genal spines; the pygidium shows 2 segments separated by a furrow. 
The author figures Sao hirsuta Barrande, pl. 8, figs. 8-1. 
Ordovician species. 
Triarthrus becki Green, 
‘Two protaspidan stages of this species have been noticed, differing chiefly in the 
size of the pygidium. Both agree in showing a strongly annulated axis, not expanded 
in front and terminating some distance within the margin. 
Acidaspis tuberculata Conrad. 
In general form the larvae resembles those of the second larvae stage of Sao, but 
the pygidium is shorter and the glabella does not expand and terminate in the anterior 
margin. No eye-line is present, but the eye lobes may be seen a little within the margin. 
The glabella has the characteristic number of annulations: margin provided with a 
row of denticles; genal angles extended into spines; pygidium with 4 spines. 
The generic term Arges Goldfuss pre-occupied. See Ceratages, Giirich, 1901, 
Arges consanguineus Clarke. 
As the main details of structure in Acidagspis and Arges are so similar the young 
Arges show the same acceleration in the development of the spines and surface orna- 
Mentation and the retention of the primitive features of the glabella, 
Proetus parvisculus Hall. 
The illustrations of this species show strongly annulated axis with groove at each 
side; large, prominent anterior eyes, pygidial pleura indicated by faint grooves, 
Dalmanties socialis Barrande. 
The author gives 4 figures of this species. 
The anaprotaspis stage showing the large, strongly annulated axis, the prominent 
anterior marginal eyes, mucronate genal angles. Pygidium of 3 segments. 
Figures 1-8 in the text illustrate the young of 4 gnostus nudus Barr. 
A, rex Barr. Trinucleus ornatus Sternb., Hydrocephalus saturnoides Barr, and H. 
Carens Barr. Olenellus (Mesonacis) asaphoides Emmons. 
— The Monophology of Triarthrus. 
Am. Jour. Sci., ser. 4, vol. 1, No. 4, 1896, pp. 251-256. 
Geol, Mag., Decade 4, vol. 3, 1896, pp. 193-197, pl. 9. 
——— Outlines of a natural classification of the Trilobites. 
Part 1, Am, Jour. Sci. ser. 4, vol. 3 
181-207, 
; , 1897, pp. 89-106, plate 3; continued on pp. 
Order Hypoparia. 
Free cheeks, forming a continuous marginal ventral plate of the head, and in some 
forms also extending over the dorsai side at the genal angles. 
Suture ventral marginal, or submarginal. 
