70 TERTIARY INSECTS OF NORTH AMERICA. 



half as broad again as the cephalothorax, nearly twice as long as broad, 

 but only half as long again as the cephalothorax, tapering apically as much 

 as if not more than basally. Legs moderately slender, short, subequal, 

 abundantly furnished with hairs and with spines, even to the tips of the 

 tarsi, especially on the two hinder pairs of legs, much as in T. ingenua and 

 with the same thinness of covering above as there, one specimen especially 

 (12977) showing it in the same marked degree as one of the preceding- 

 species. As there also, all the specimens appear to be females. 



Length of body, 7.1"™; cephalothorax, 2.3™"'; cheUceres, 1.5°""; abdo- 

 men, 5™"'; breadth of cephalothorax anteriorly, 1.4"""'; greatest breadth, 

 2.1™"; breadth of abdomen, 2.75'""; length of first pair of legs, 7™"'; sec- 

 ond pair, 7.3'""' ; third pair, 5.5'""' ; fourth pair, 8™"'. 



The slenderer form of the whole body and the less disparity in size 

 between the cephalothorax and abdomen mark this species as distinct from 

 the preceding. 



Florissant. Four ?, Nos. 5656, 12006, 12977, and Princeton collec- 

 tion, No 1.809. 



Suborder RETITELARI^ Thorell. 



Next to the last equivalent group, these spiders, which make a loose 

 wel) or snare apparently constructed without any regular plan, are the 

 most numerous in Tertiary deposits, forming in Europe, as we have seen, 

 29 per cent of the total fauna. This, as before, is dependent in large 

 measure upon their representation in amber, which contains forty-eight of 

 the fifty-five described species. The number known fi'orn the European 

 strata is, however, greater than in any other of the larger groups, while 

 the American species of the same here brought to light are for once con- 

 siderably less numerous than the European, All the species belong to 

 the Theridides, which is also far the richest in forms at the present day. 

 (November, 1881.) 



Family THERIDIDES Koch. 



There is no single family of spiders so abundantly represented in Ter- 

 tiary deposits as the Theridides. No less than fifty-four species, or more 

 than one-fourth the whole number of fossil Araneides of Europe, belong to 

 this group and represent fourteen genera. Theridiixm is richest, with six- 

 teen species ; then follow Thyelia with eleven ; Zilla, Micryphantes, and 



