Palaeozoic Arachnida of North America. 



53 



Family Isobuthidae. 



Palaeohuthus n. gen. 



Sternum triangular. Third coxae abutting against the sternum, 



fourth against the ellipsoidal genital operculum. Abdominal s-ter- 



nites with straight posterior edges. Genotype P. distinctus n. sp. 



Palaeohuthus distinctus n. sp. 

 Plate I, fig. 5 ; text fig. i6. 



The nodule containing the type and only specimen of the species 

 and genus consists of two halves the one of which is so badly de- 

 formed that nothing can be made out 

 clearly. The obverse, however, is very 

 well preserved and shows the sternum, 

 genital operculum, comb, abdomen, four 

 and a third post-abdominal segments, 

 third and fourth pairs of coxae, and frag- 

 ments of legs. No traces of other appen- 

 dages are left, but for a part of the tibia 

 with finger of the right pedipalp on the 

 obverse, showing that the specimen had 

 a narrow hand with probably long fingers. 



The sternum is small, triangular, with 

 a spine-like projection running between the 

 second pair of coxae. The genital oper- 

 culum is transversely ellipsoidal, w^ider 

 than the base of the sternum. Against it 

 are abutting the ends of the fourth coxae. 

 The comb is clearly defined, but the teeth 

 do not show the hues between them and 

 therefore cannot be counted . The abdomen 

 is 22.0 mm. long from base of the genital 

 operculum to end of last sternite. The 

 second sternite is by far the longest. The posterior edge of all sternites is 

 entire, almost straight and not bilobed as in Eohuthus. The four post- 

 abdominal segments measure together 17.0 mm. Length of straight 

 line from genital operculum to base of hand 23.0 mm. Length of 

 visible fragment of hand with finger 5.5 mm., width of hand 1.8 mm. 

 Probable length of specimen 55 mm. The whole body is smooth. 



No. 133 in the collection of the Peabody Museum. 



Found in the Pennsylvanic (Lower Allegheny) of Mazon Creek, 

 Illinois. 



Fig. 16. 

 Figure 16. — Palaeohuthus dis- 

 tinctus n. sp., holotype, Pea- 

 body Mus. No. 133, ventral 

 surface. X 



1.6 



