508 R. I. Pocock—Carboniferous Arachnida. 
of the femur is twice the length of the distal, whereas in the last 
two it is only one-third of the length. Since the femora are some- 
times segmented in the Chelonethi (Pseudoscorpiones), it would he 
rash to reject unhesitatingly on «@ priort grounds Fritsch’s restoration 
of the legs in Anthracomartus ; but since the legs of the specimens 
of the genus that I have seen, as well as of the allied genera 
Eophrynus and Anthracosiro, have normal and unsegmented femora 
like a great majority of the Arachnida, there can be very little 
doubt, I imagine, that Fritsch has mistaken fortuitous cracks for 
intersegmental joints. And this is by no means a solitary case 
where a knowledge of the constancy of certain morphological features 
in the Arachnida enforces the imposition of such an interpretation 
upon his restorations. 
2. On THE STRUCTURE AND CLASSIFICATION OF THE PHALANGIOTARBI. 
The name Phalangiotarbi was proposed by Haase in 1890 for 
a group accorded subordinal rank under the Opiliones. It contained 
the genus Phalangiotarbus created for the species described by 
Dr. Henry Woodward as Architarbus subovalis. I agree with Haase 
in thinking the type-species of Architarbus and Phalangiotarbus 
generically distinct, and with Fritsch in regarding them as belonging 
to the same order of Arachnida. But whereas Fritsch referred them to 
a family of Opiliones, the Architarbide, it appears to me necessary 
to give them higher systematic rank. I therefore retain the term 
Phalangiotarbi, leaving open for the moment the question of their 
right to inclusion in the Opiliones. In addition to the genera just 
mentioned I assign to this group Geratarbus, Geraphrynus, and the 
new genus Opiliotarbus described below. 
The morphology of this series of genera has hitherto baffled 
research ; and I am indebted to well-preserved material kindly lent 
to me by Dr. Wheelton Hind, Mr. 8. Priest, the late Mr. W. Madeley, 
Mr. H. Johnson, F.G.S., and Mr. Walter Egginton for the new inter- 
_ pretation of the facts set forth in the following pages. 
Since more than one species has in some cases been referred to the 
genera, I take this opportunity of stating that the type-species of 
each is as follows: Architarbus, Scudder, 1868; type, A. rotundatus, 
Seudder. Geraphrynus, Scudder, 1884; type, G. carbonarius, Scudder. 
Geratarbus, Scudder, 1890; type, now selected, G. dacoez, Scudder. 
Phalangiotarbus, Haase, 1890; type, Architarbus subovalis, H. Woodw. 
Opiliotarbus, nov.; type, Architarbus elongatus, Scudder. 
In the diagnosis of Geraphrynus published by Scudder in 1890, the 
genus is said to possess a ‘‘ posterior shield of the cephalothorax, the 
anterior triangular fragment of which slopes upwards to the ridge 
[of the cephalothorax ], while the hinder portions with their transverse 
scorings and ridgings lie on a plane below .. . this post-thoracic 
plate crowds down the middle of the six following segments”’. 
Comparing the dorsal and ventral views of my specimens of 
Geraphrynus with Scudder’s figure of G. carbonarius, I am forced to 
conclude that the so-called post-thoracic plate has no existence as 
such, but is composed of the anterior two or three sternal plates of 
the opisthosoma and the posterior projection of the carapace. It is 
