ft%^ Zoological Society, 



externo pedum primi 'parts longitudine clypeum excedente ; 

 corporis postica parte longissima, cylindrica. 



Long, toti corporis 1-5 poll., clypei '65 poll. ; lat. clypei */ poll. 



Apus longicaudatus^ Le Conte, Ann. Lye. Nat. Hist. iv. 155. t. 9. 



Hah. 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 "3 poll. ; lat. clypei '4 1 poll. 



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



Hah. 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 

 evaporation and infiltration, and were now crowded to excess, prin- 

 cipally with the Apus, great numbers of which were dying upon the 

 surrounding mud, whence the water had receded. This species is 

 distinguished from the productus of Bosc and Montagui of Leach, 

 by not having the dorsal carina prolonged in a point behind ; and 

 from cancriformis by the greater proportional width of the thorax, 

 and more obtuse emargination behind. The length of the thorax along 

 the middle is three-tenths of an inch and its greatest breadth some- 

 what more. It may be named Apus obtusus.'' — Note 7. p. 336. 



5. Apus Domingensis, Baird, sp. nov. Clypeo corporis dimidiam 

 partem tegente, rotundo, tenui, corneo ; ramo externo pedum 

 primi paris corpus cequante. 



Long, toti corporis 1 poll. ; lat. clypei J poll. 

 Hah. In Insula St. Domingo, India Occidentali. CoUegit M. Sall^. 

 Museum Britannicum. 



Though a native of the West Indies, this species may be easily 



