1874.J lOJ [Cope. 



Radial formula, D. YII. 17 ; A. 12 ; P. 15 all simple ; Br. VI. The 

 liead is depressed and enters the length minus the caudal fin, three 

 times. Orbit large one-fifth length of head, and twice the width of 

 the fi'ontal interspace. Greatest depth (at first anal ray) 6.75 times in 

 length less caudal fin. Anal commencing opposite the third ray of the 

 second dorsal. Lateral Hue deflexed opposite last ray of second dorsal- 

 The recurved preopercular spine strong, the decurved small and obtuse. 

 Palatine teeth present ; end of maxillary reaching line of pupil. Isthmus 

 as wide as length of muzzle and orbit to front line of pupil. Skin every- 

 where smooth. 



Total length .084 ; do. less caudal fin .069 ; do. to anal .042; do. to 

 first dorsal .031 ; of head .022 ; width at maxillaries distally .0125 ; at 

 preopercular spines .0185. 



From Beaver river S. W. Utah. The other species of the Rocky 

 Mou.nt2iins, IK punctulata, Gill, has, according to that zoologist a much 

 wider head, especially in the frontal region. This character is well ex- 

 hibited by specimens in Dr. Hayden's collections. 



Dedicated to Lieut. Wheeler, Director of the U. S. Survey west of the 

 100th Meridian. 



ON THE ZOOLOGY OF A TEMPORARY POOL ON THE PLAINS 

 OF COLORADO. 



By Prof. E. D. Cope. 



{Bead before the American PMlosopMeal Society, Marcli 20th, 1874.) 



Some years ago, Thomas Kite, of Cincinnati, observed an Entomostra- 

 cous crustacean swimming in a temporary pool of I'ain-water. A species 

 no larger than a pin's head is abundant in horse-troughs, springs, &c., 

 and belongs to the genus Cypris. That observed by Mr. Kite is much 

 larger, and is not known to occur in flowing water. It was named 

 Limnadella Kitei by Girard. I have since observed it in Pennsylvania, 

 in rain puddles standing in the ruts of roads in woods ; and in New 

 Jersey Dr. Knieskern found it in similar pools alongside of roads 

 in the open country. The wonder naturally is, how strictly aquatic 

 branchiferous animals can be propagated under the circumstances, and 

 how they can be distributed from place to place. A similar species has been 

 recently observed by M. Tissandier in pools in the valley of the Seine. 

 These were left by a flood of the river, and before drying up became 

 populous with a species of the Cyprididaa. 



The most remarkable examples of this kind are, however, to be ob- 

 served on the plains of Kansas and Colorado. 



Here rains create temporary pools in depressions of the surface, which 

 may remain for a few days or weeks, but are all dried up by the end of 

 September. Nevertheless, some of them at least swarm with a population 

 of branchiferous crustaceans, worms and larvaj of insects, with the adults, 

 which, in their developed state, come to the surface for air, or live on 



