PACKARD ON A NEW CAVE FAUNA IN UTAH. 165 



cle on the fourth joint ; the three other pairs are unarmed. Second pair 

 of legs longer than the first by one- third of their length. The second 

 and fourth pairs are of nearly equal length, the fourth pair differing in 

 having the third joint considerably swollen. The third and first pairs of 

 the same length. On the coxai of the second pair of legs is a pair of stout 

 conical spines, meeting over the median line of the body. The anterior 

 tarsi are 3-jointed, as in S. terricola of Europe, the middle one much 

 shorter than the other two, which are of equal length. Those of the 

 second pair 5-jointed, those of the third and fourth pairs 4-jointed, the 

 end of the tibise bein g constituted so that the limbs appear as if they 

 had five tarsal joints. Ungues rather long and moderately curved. The 

 legs are stouter and shorter than in S. terricola, and none of my speci 

 mens have the long, singular, sinuate appendage on the first joint pres- 

 ent in S. terricola. (They are not referred to by M. Simon in his de- 

 scription, though my specimens were received from him.) 



Length of body, exclusive of the mandibles, S.S™"^; breadth, 2.5™™. 



Compared with S. terricola Simon from Corsica, which also lives under 

 very large stones, and is found common at Porto-Vecchio after the heavy 

 spring rains, but which has not yet occurred in caves, our out-of-door form 

 is much stouter, with much shorter legs, and also differs in its well-devel- 

 oped eyes, dark brick-red tegument, and dark markings. It was dis- 

 covered in Colorado in 1874 by Mr. Ernest Ingersoll, while attached to 

 Hayden's Geological Survey of the Territories. He tells me that it did 

 not occur in any cave, the exact locality and mode of life being forgotten- 

 It will most probably be found under stones. 



Compared with Scotolemon Jlavescens {Erebomaster flavescens Cope, 

 American Naturalist, vi, 420, 1872, from Wyandotte Cave, Indiana), 

 which is allied to the European S. piocharcli which inhabits caves near 

 Orduno, it differs in the basal segments being much more distinct, where 

 the sutures in the tergum are obsolete in S. Jlavescens. The eye-tubercle 

 is a little smaller proportionately, while the eyes themselves are much 

 larger. The mandibles and maxillse are shorter, while the legs are very 

 much shorter and stouter. The color is deep-red, the cave species being 

 pale-yellow. These are all differences such as we should expect to find 

 between a cave-dweller and one which has lived out of doors under 

 stones, &c. In these two species, we have forcibly brought before us the 

 great structural differences brought about by striking differences in the 

 environment of the two species. 



A high degree of interest attaches to this cave fauna, because we are 

 able to determine with much i:)recision the period when the cave was 

 made, and the time of its subsequent colonization by the ancestors 

 of the present inhabitants. On turning up the loose material con- 

 stituting the bottom of the cave, I found that it was largely com- 

 posed of a shell-marl, in which occurred in abundance little fresh- 

 water shells which Mr. G. W. Trvou determines as Amnicola decisa 



