296 GEOLOGICAL SURVEY OF THE TERRITOEIES. 



Prof. A. E. Vsrrill, Mr. Edward Burgess, Dr. E. Ooaes; acknowledg- 

 ments of whose valnable aid are made iu tlieir appropriate places. 



In the following pages I have touched upon some points in the inter- 

 nal anatomy of these interesting Crustacea, and only regret that want 

 of time has prevented me from entering more into detail. For a num- 

 ber of microscopic slides of Branchipus, Thamnocei>halus, Estheria, 

 &c., I am much indebted to the friendly aid and skill of Noiman IST. 

 Mason, esq., of Providence, E. I. 



I desire also to express my thanks to Prof. F. V. Hayden, for the kind 

 interest which he has taken in this work, and for the liberal number of 

 plates with which the essay has been illustrated. 



The chapter on the development of the young of Apus lucasanuft and 

 Streptoccplialus texanus has been contributed by Dr. 0. F. Gissler, of 

 Brooklyn, IsT. Y., who made the draAvings which illustrate the text, and 

 also those composing Plates XXXIV and XXXV. A number of the 

 drawings of the entire animal of the species of Apus and Lepidurus, 

 &c., were made by Mr. J. H. Emerton ; some anatomical drawings in 

 the plates were prepared by Mr. J. S. Kingley, while I am under oljliga- 

 tions to Mr. Edward Burgess for the masterly manner in which he has 

 executed the difficult sketches of the animals of Limnetis hrevifrons, 

 Estheria of several species, Eulimnadia, and Branchipus vernalis. 



I. CLASSIFICATIOX OF THE LIVmG PHYLLOPODA. 



HISTORY OF THE SUBORDER PHYLLOPODA. 



The history of this group is an interesting one. Originally mentioned 

 in 1785, by O. F, Mviller, in his '•'■Entomostraca sen Insecta testacea,^^ the 

 Entomostraca were first defined in 1806, by Latreille, in his Genera Cms- 

 taceorum, &g. Under Legio prima, Entomostraca, the PhyUopoda con- 

 stituted the third order, the sole representative of this order being 

 Apus, while the genus Brancliiopoda (Branchipus of Schoeffer) forms 

 part of a sixth order, Ceplialota. The other genera of Phyllopods were 

 not then known. 



In 1820, Brongniart proposed the genus Limnadia for Hermann's 

 Daplmia gigas (1804). 



Meanwhile in 1817, in the first edition of Cuvier's Eegne Animal, the 

 order Brancliiopoda was proposed by Latreille, while the classification of 

 this order was farther amended and improved in the second edition of 

 this work (1829). In this edition the PhyUopoda constitute the second 

 suborder of the Branchiopoda, and now the Phyllopods comprise the 

 genera TAmnadia, Branchipus, Artemia, and Apus. 



In 1837, Straus-Durckheim described the genus Estheria, of which 

 Cyzicus of Audouin (1837) and Isaura Joly (1842) are synonyms. The 

 genus Limnetis was described by Loven iu 1845. 



In 1840, Milne-Edwards, in his Histoire Naturelle des Crustaces, es- 

 tablished the Legion Branchiopodes, equivalent to the Entomostraces. 

 Under the Branchiopoda he regards the PhyUopoda as forming an order, 

 and they are succeeded by the Cladocera, while the Legion of Entomo- 

 straca comprises the Ostracoda and Copepoda. 



In 1853, Prof. J. D. Dana, in the Crustacea of the United States Ex- 

 ploring Expedition, regarded the PhyUopoda as constituting tlie second 

 Legion of his first order {Onathostomata) of Entomostraca. 



In 1863, Gerstaecker regarded the PhyUopoda as forming a family of 

 the order Branchiopoda, the Trilohifa, Cladocera, and Ostracoda, forming 

 tlie remaining families. ClauSj in 1868 (Grundzlige der Zoologie), divided 



