510 R. I. Pocock— Carboniferous Arachnida. 
carapace is large, unsegmented, and has either a straight or convex or 
considerably produced posterior border; at least, the coxe of the four 
posterior pairs of appendages are large and radiate from a central 
broader or narrower sternal area. The dorsal surface of the 
opisthosoma consists of five or six straight or curved but always 
short or very short anterior terga, and of three or four much longer 
posterior terga; and the ventral surface of seven, possibly eight, sternal 
plates, of which the posterior are long and the anterior short, the 
first being triangular and wedged between the coxe of the last 
pair of legs. ; 
The following notes on the genera above mentioned will explain my 
reasons for admitting them :— 
1. In Phalangiotarbus subovalis the anterior five terga of the 
opisthosoma are short and straight, and the posterior three large, there 
being eight in all. The posterior border of the carapace is straight, 
the anterior border widely rounded. The chief peculiarities of the 
genus, however, lie in the facts that the sternal area of the prosoma is 
large and oval and that the coxee of the legs of the first pair do not meet 
in the middle line beneath those of the palpi. Only one specimen of 
this genus has been discovered, and I judge of its character from the 
figure published by Dr. Woodward. 
2. Architarbus, represented by the single species rotundatus, has 
the carapace rounded in front and strongly produced in the middle 
line behind, with the anterior terga of the opisthosoma curved round 
its bulging area. There are nine terga in the opisthosoma, and they 
appear to increase progressively in length from before backwards, the 
anterior five or six being short. ‘The sternal area of the prosoma is 
small and subcircular, and round it radiate four pairs of coxee of the 
ambulatory limbs, those of the first pair meeting in the middle line 
and concealing the basal segments of the palpi. This species is only 
known to me from Scudder’s figure and description. 
3. Geraphrynus has the carapace angular in front and convex or 
produced behind. The opisthosoma has nine terga, the posterior three 
being much longer than the anterior six, two or more of which follow 
the curvature of the carapace. The sternal area of the prosoma is 
long and narrow, and the coxee of the legs of the first pair meet in 
the middle line and underlie those of the palpi, as in Architarbus. 
From the latter Geraphrynus seems to be separable by the anterior 
angulation of the carapace, the long and narrow sternal area of the 
opisthosoma, and the marked enlargement of the posterior three terga 
of the opisthosoma. When characterized in 1884' this genus was 
based upon a single species represented by a specimen from Mazon 
Creek, Illinois. In 1890 the species was redescribed by Scudder,’ 
several additional specimens being used for the purpose, but it is quite 
clear from the context that the example illustrated by fig. 10, pl. xl of 
the later work is the type. It is from the figure and description of 
this specimen and from examples of other species in my hands that the 
characters of the genus have been taken. Beyond recording my belief 
1 Proc. Amer. Acad. Arts & Sci., vol. xx, pp. 17-18. 
* Mem. Bost. Soc. Nat. Hist., vol. iv, pp. 446-7. 
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