THE CAMBRIAN FAUNAS OF NORTH-EASTERN AUSTRALIA. 
119 
At the present time it would be preferable to use the name Dorypyge 
with hesitation for late Middle Cambrian species that have non-granulate tests 
or axial pygidial spines. Of the remaining forms that, with more confidence, 
may be left in Dorypyge the genotype, D. richthofen Dames (1883, p. 24, pi. 1, 
figs. 1-6), has the most primitive characters, in that there are traces of glabellar 
furrows, while the lateral ribs of the pygidium are divided by grooves that 
Lake (1938, p. 251) satisfactorily interprets as rudiments of the original pleural 
sutures. 
Attention may be called to the pair of pits on the axial furrow of the 
cephalon of most species of Dorypyge. Pits in this anterior position, near 
the junction of the axial furrow and the palpebral ridges, are known in many 
trilobites. In certain forms, for instance Dinesus and the members of the 
family Nepeidae, anterior grooves radiate from these portions. Such pits or 
grooves on the surface become elevations on the inside of the test and I would 
suggest that, like the structures in the axial furrows of the thorax of many 
trilobites, they mark the place of attachment of muscles. One possible 
explanation is that they represent the places where the muscles controlling 
the antennules were attached. One specimen of Dorypyge tenella in the present 
collection is known from an excellent ventral surface of the head ; and on it 
the centre of each elevation (that corresponds ventrally to the pit) bears a 
central depression. 
The species of Dorypyge now recorded from Australia are a species group 
with similarities in such features as the more strongly accentuated fifth pair 
of pygidial spines and the presence of a sixth (posterior) pair that are mere 
rudiments. As a group it most closely resembles the Asiatic (Chinese and 
Manchurian) forms. 
It is reasonable to suggest that Dorypyge and the similar forms of the 
later Middle Cambrian with axial spines on the pygidium may be the descendants 
of Kootenia and N otasaphus of the early Middle Cambrian. In those two genera, 
as previously noted (Whitehouse, 1939, p. 241), the stock seems to have 
differentiated into at least two groups — one (N otasaphus) without axial spines 
on the pygidium and another ( Kootenia ) having such spines. Dorypyge there- 
fore may be the successor of N otasaphus ; and the unnamed group typified 
by D. lakei may be more allied to Kootenia. Other variants (e.g. D. omens) 
seem to have affinities with still other members of that rather variable earlier 
group. If so, the whole Middle Cambrian assemblage (Dorypygidae) may 
represent a gradually diverging stock of related forms. 
DORYPYGE TENELLA sp. nov. 
(PI. XI, figs. 1-5.) 
Diagnosis : Cranidium and pygidium ornamented with very fine, closely 
packed, hollow granules that, however, are absent from the furrows. 
The cranidium is subquadrate with a slightly convex anterior margin. 
The glabella, which is inflated and unfurrowed, has sides that are parallel or 
only very slightly divergent and a sharply truncate anterior ; it reaches almost 
to the anterior border, the anterior rim being particularly narrow; the axial 
