Tertiary Spiders and Opilionids. 249 



FAMILY THOMISID.'E (lATERIGRADAe) . 



Characters of the Family : — Eight eyes in two rows, all diurnal, 

 lateral eyes largest. Legs modified for lateral, crab-like locomo- 

 tion. Tarsi with two claws, with ungual tufts. Spinnerets con- 

 tiguous, with a distinct colulus in front of them. 



Although several groups of spiders have laterigrade l9comotion, 

 the Thomisids are usually easily recognizable. Usually they are 

 smaller than either the Selenopidse or the Heteropodidae and are 

 distinguishable from the former by the position of the eyes and 

 from the latter by the structure of the metatarsi. Moreover 

 neither of these has a colulus. The generic distinction of Thomi- 

 sids involves the study of the maxillary lobes, lip, sternum, mar- 

 gines of chelicerse, hair etc., all characters not sufficiently apparent 

 or completely indiscernible in extinct specimens. The three spe- 

 cies which Scudder refers to the genus Tlioinisiis are unquestion- 

 ably Thomisids and his choice of genus is fortunate, for we may 

 again regard it as merely a representative, indeterminate genus. 



Genus Tlwinisus Walckenaer. 



Tlwiiiisiis resiitus Scudder. 



Scudder, Tertiary Insects, 1890, p. 57, Plate 11, fig. 13. 



A single specimen of uncertain sex from Florissant, Nos. 5502 



(now No. 68) and 7521 in the Scudder Collection of the Museum 



of Comparative Zoology of Harvard University. 



The specimen is poorly preserved and its description given by 

 Scudder is correct in all details. 



Tlwinisus disjunctns Scudder. 

 Scudder, Tertiary Insects, 1890, p. 58, Plate 11, fig. 9. 



Scudder describes two specimens from Florissant, one No. 9677 

 (now No. 69) in the Scudder Collection of the Museum of Com- 

 parative Zoology of Harvard University, the other No. 10377 

 which I have not seen. 



Scudder's description is correct except for his statement that 

 "the tibiae and first tarsal joint are completely consolidated into a 

 single piece, so that the line of demarkation can not be seen." 

 Examination of the legs under higher power reveals the pres- 



