132 AMERICAN SPIDERS 



comprises a single known species having about the same range as its 

 congener, the turret spider, and sometimes found in the same col- 

 onies. The burrow of Aliatypus calif ornicus is comparatively long, 

 and either goes straight down into the compact soil or is provided 

 with pronounced bends. The silken lining is quite thin, but thickens 

 around the opening, which is covered with a trap door of the 

 wafer type. The burrows are usually found along roadside banks 

 and streams, where the spider seems to prefer exposed soil only 

 thinly covered with vegetation. 



The female Aliatypus resembles the turret spider, but has a some- 

 what broader carapace marked by a round median groove. The 

 male resembles the female quite closely, and completely lacks a 

 distinctive spur on the chelicerae such as is present in Atypoides. 

 The male palpi are thin appendages fully as long as the first pair of 

 legs. In this genus the most interesting characteristic is that the 

 anterior lateral spinnerets are nearly equal in size to the posterior 

 median, and are also two-jointed. Well-developed spigots show 

 that they are still functional appendages a fact that marks them as 

 the most generalized of all mygalomorph spinnerets, except those 

 of the Liphistiidae. Since they are bisegmented, we can state with 

 confidence that they are definitely the anterior lateral pair, and 

 thus corroborate on direct evidence what has been the presumption 

 of the majority of araneologists. 



The type genus of the family Antrodiaetus is in many respects 

 the most highly developed. The short anterior lateral spinnerets, 

 greatly reduced in size in Atypoides, have here been completely 

 lost. The carapace has the median groove present as a longitudinal 

 impression. In the males the abdominal dorsum has three distinct 

 tergites above the base, and in the females one or more is present. 

 The chelicerae of the males are armed with a prominent tubercle 

 set with black setae. 



These spiders live in burrows, which may descend a foot or 

 more in the soil, and which often have prominent bends. The upper 

 part of the burrow is usually well lined with silk; in western species 

 the opening is often concealed under stones or hidden in debris. 

 As a result of their secretive habits and their well-hidden burrows, 

 relatively few females are known in collections, whereas the males, 

 which rove around in the late summer, are quite common. An ex- 

 ception may be made for some .eastern species that dig their nests 

 right in the open, and are easy to find. 



About a dozen species of Antrodiaetus have been described from 



