ARAOHNIDES— ARANEIDES— LATERIGRAD^. 57 



THOMISUS Walckenaer. 



Three species of Thomisides occur in the Tertiaries of Colorado, and 

 apparently all of them (one is mutilated) belong to tho true Thomisinse, in 

 which the hinder two pairs of legs are much weaker than the others. As 

 the cephalothorax is in all cases poorly preserved or lost, it is impossible to 

 speak at all definitely of their generic relations, and therefore I have placed 

 all of them in the typical genus Thomisus, from which the family derives 

 its name, and which, or Xysticus, its near ally, they closely resemble in 

 general appearance. In all the abdomen is nearly round. It is interesting 

 to find, as observed above, tliat the species of this family from the stratified 

 deposits of the European Tertiaries have also been placed in Thomisus and 

 Xysticus, though none of them appear to be very closely allied to our 

 species. 



This genus is widely spread, but nearly all the species belong to the 

 warm temperate regions of Europe and North America. (November, 1881.) 



Table of the species of Thomisus. 



Tibiae of hinderpairsof legs broader at tip than at base, and much broader than the tarsi. ..1. T. resutus. 

 Tibiie of hinder pairs of legs of e<iual width throughout. 



Small species; femora of first pair of legs half as long again as those of second pair; tarsi as Ijroad 



as the tibiae 2. T.disjunclus. 



Large .species; femora of first and second pairs of legs of about equal length; last tarsal joint 

 slenderer than the tibise . 3. T. defossita. 



1. Thomisus resutus. 



PI. 11, Fig. 13. 



Abdomen plump, short ovate, about a fourth longer again than broad, 

 the base broad, the sides well rounded, the hinder extremity full, with the 

 extreme apex squarely truncate. Only a fragment of the cephalothorax 

 remains, showing the broad attachment of the abdomen. The two hinder 

 pairs of legs only are preserved, showing limbs of considerable length, bent 

 forward, the femora nearly as long as the abdomen, longer than the tibiae 

 and flattened, largest in the middle; the tibife are straight, completely con- 

 solidated with the first tarsal joint as in spiders generally, also flattened, 

 slender at base and gradually though slightly increasing in size apically, a 

 peculiarity which is not shown in the plate; the tarsi are much slenderer, 

 not flattened, and longer than the tibiae, the first joint alone being nearly as 



