GERAPHRYNUS. 47 



The type and only known specimen of this species, which is known to me 

 solely from the figure and description, is imbedded in an ironstone nodule from 

 the Coal Measures of Lancashire. 



Family ARCHTTARBiDiE, Karsch. 



Sternal area of prosoma small, and either subcircular or more usually narrow 

 and elongate, the proximal ends of the coxa? being close together ; the distal ends 

 of the coxae not, or hardly, overlapped by the edge of the carapace. Coxae of palpi 

 usually, at all events, entirely concealed from below by those of the legs of the first 

 pair, which meet throughout their length in the middle line ; only in Geratarbus do 

 they appear to be in contact at their proximal ends, and diverge to a slight extent 

 outwards, leaving a narrow space between. Coxse of legs of fourth pair also 

 meeting, or almost meeting proxiinally behind the posterior end of the sternal 

 area. Opisthosoma with eight or nine tergal plates. 



This family, in the sense in which I have recently defined it (Geol. Mag. [5], 

 vol. vii, p. 512), contains several genera, of which only one, Geraphrynus, is known 

 to be British, the others, namely, Arcldtarbus, Scudder, Geratarbus, Scudder, and 

 OpiHotarbus, Pocock, having been recorded from North America. 



Genus GERAPHRYNUS, Scudder. 



1884. Geraphrynus, S. H. Scudder, Proc. Amer. Acad. Arts Sci., vol. xx, p. 16. 



1890. Geraphrynus, S. H. Scudder, Mem. Bost. Soc. Nat. Hist., vol. iv, p. 445. 



1904. Geraphrynus, A. Fritsch, Palseoz. Araclm., p. 33 (in part). 



1910. Geraphrynus, E. I. Pocock, Geol. Mag. [5], vol. vii, pp. 510, 512. 



Generic Characters. — Body typically wide, its width across the anterior half of 

 the opisthosoma nearly half the total length. Carapace usually angular in front, 

 with its anterior lateral margins convex and gradually diverging to the posterior 

 lateral angles, where the plate is widest ; its posterior border either evenly convex 

 or produced posteriorly in the middle. A pair of median eyes near the anterior 

 extremity. Opisthosoma with nine tergal plates, the first two or more following 

 the curvature of the posterior border of the carapace ; the sixth segment much 

 shorter than the seventh, and generally a little, sometimes markedly, longer than 

 the fifth. A sulcus commonly traceable on each side of the terga, extending from 

 a point not far from the postero-lateral angles of the carapace to the convex 

 posterior border of the ninth plate, terminating one on each side of the anal 

 orifice, and dividing the terga into three areas, a median and two lateral. The 

 anal orifice subapical, and probably closed by a small opercular plate representing 



