SPIDERS. 11 



of the weaving spiders. One of them, however, is very remark- 

 able, and seems to Prof. Heer to represent an extinct genus 

 (Schellenbergia rotundata, fig. 211), characterized by short palpi 

 with a large globular apical joint, a short nearly globular abdo- 

 men, closely adpressed to the cephalothorax and marked with 

 transverse impressions. The legs of the third pair are the 

 shortest ; and the rest are nearly of equal length. The femora 

 are traversed by a longitudinal rib. This is the only spider 

 found at CEningen which differs considerably from living genera ', 

 the others have little that is remarkable about them, and belong 

 chiefly to genera which have at present a very wide distribution. 

 Most of them probably lived on the banks of the Lake of (Enin- 

 gen, the cross-spider spreading its net between the reeds and 

 rushes, the crab spiders attaching their flat sacks to the marsh- 

 plants, on the flowers of which they sunned themselves and lay 

 in wait for insects, the weavers stretching their horizontal nets 

 on plants and trees, after the fashion of their living relatives, and 

 the lurking spiders and Macaria dwelling under the bark of trees 

 and under stones. All these spiders consequently lived on land, 

 and got accidentally into the water, where they were enveloped 

 by its mud; but one species (Argyronectat longipes) probably* 

 lived in the water, and represents the remarkable water-spider 

 A. aquatica, Deg., which also occurs in Switzerland (as in the 

 Katzensee). This spider builds in the water a sack-like nest of 

 silk with the opening downwards. This it fills with air by the 

 following process : the spider comes to the surface and raises 

 its hairy abdomen above tfce water, and then, suddenly diving 

 down, carries with it the adherent air-bubbles, which it sweeps 

 off" with its legs after reaching the interior of its nest. Although 

 its respiratory apparatus does not differ from that of other spi- 

 ders, the air surrounding its abdomen enables it to carry on its 

 operations under water. 



* Unfortunately the two specimens which Prof. Heer received are not suf- 

 ficiently well preserved for certain determination. The comparative lengths 

 of the legs, the thin filiform palpi, and the rounded form of the sides of the 

 cephalothorax are in favour of its being referred to Argyronecta, but the 

 cephalothorax is less prominent in front than in the existing species. A 

 similar form of cephalothorax and legs also occurs in Tegenaria. According 

 to Thorell this species does not belong to Argyronecta, but seems to form a 

 distinct genus ; this is also the case with the Clubiona. 



