Hab. In Insula "St. Vincent's," India Occidentali ; Rev. Lans- 

 downe Giiildinff. 



Mr. Thompson in his ' Zoological Researches ' remarks : " I re- 

 ceived this species of Apus together with the Artemis Guildingi 

 from the West Indies, and having as yet no details, must leave its 

 history in the hands of its distinguished discoverer. It is of a light 

 hlackish colour, the clypeus translucent, almost membranous, and 

 shorter in proportion than in any of the known species, with the 

 extreme branch of the anterior member extremely long." Unfor- 

 tunately we have no further history of this species from its discoverer 

 the Rev. Lansdowne Guilding, but the short square-shaped cara- 

 pace and the extreme length of the external branch of the first pair 

 of feet sufficiently distinguish it. 



3. Apus longicaudatus, Le Conte. Clypeo corporis tertiam 

 partem non multo magis tegente, rotundato, subfusco ; ramo 

 externa pedum primi parts longitudine clypeum excedente ; 

 corporis postica parte longissima, cylindrica. 



Long, toti corporis TS poll., clypei '65 poll. ; lat. clypei '7 poll. 



Apus longicaudatus, Le Conte, Ann. Lye. Nat. Hist. iv. 15.5. t. 9. 



Hab. In America boreali. " In a shallow lake on the high plateau 

 between Lodgepole Creek and Crow Creek, N.E. of Long's Peak" 

 {Le Conte). 



This species is readily distinguished by the extraordinary length 

 of the abdominal portion of the body. The carapace is rounded, 

 somewhat truncated at the anterior extremity, and having the two 

 extremities of the fork terminating in a very sharp point. It does 

 not cover much more than one-third of the body, and is thin in 

 substance. The external branch of the first pair of feet is long, ex- 

 ceeding considerably the length of the carapace. The caudal fila- 

 ments are about the length of the abdomen. Mr. Le Conte says 

 that the species was found in immense numbers in a small shallow 

 lake on the high plateau between Lodgepole Creek and Crow Creek, 

 N.E. of Long's Peak, near the Rocky Mountains. "They were 

 swimming about with great activity, plunging to the bottom and 

 rising to the surface." 



4. Apus obtusus, James. Species hcec reperta a Domino James 

 in " Major Long's Expedition to the Rocky Mountains," non 

 satis bene descripta necnon delineata est. 



Long, clypei 'S poll. ; lat. clypei "4 ? poll. 



Apus obtusus, James, Expedition to the Rocky Mountains, ii. 336. 



Hab. In America boreali. " Rain-water puddles on the Platte 

 river, near the Rocky Mountains" {James). 



This species is very briefly described by Mr. James. " In rain- 

 water puddles," he says, " we remarked a new species of Branchio- 

 pode belonging to the genus Apus ; small crustaceous animals, which 

 exhibit a miniature resemblance to the King or Horse-shoe Crab 

 {Limulus polyphemus) of our own sea-coast, but which are furnished 

 with about 60 pairs of feet, and swim upon their back. The basins 

 of water which contained them had been very much diminished by 



