STATE GEOLOGIST. 



15 



page is growing obliquely upward. The Daphnidge are represented 

 as expanding upon the same plane as Moiua, and the Lyncodaph- 

 nidce extend diagonally downward, producing the Lynceid branch 

 The Bosminidffi spring from the stem at a lower point. These 

 relations are made obvious by the figure giving a view of the ideal 

 tree as seen from the side.* 



Umaosida 



Sohpedidss 



^-SJda. 



PseudoSida 



• ^ .— *" 



,DaphnelLa 



,Latona 



(?; 



<SID'ID/€> 



I 

 I 

 r 



Bosmlaa. 



~~ MOINA Ceriodaphnia 



<lyncodAphnid/e> 



Streblocercus f^acrothrif v^ 



Simo^ephalus 

 / "Daphnist 



^ Scapho/e hen's 



I 



iV 



Lyncodaphnia 

 I 

 I 



LathoiiMra 



Drepanothri/ ^ v-' — 



> "x 



I 



I 



- /liocryptUS 



SIDIB>E L^ 



Acantholeberis ^ClYNCEID/E) \ 



_ Eurycercus ^^ '^'^ 

 Camptocercus y y^ 



Alonopsis'' 



^ 



lAlona) y 

 Lynceus 



{ F/eOroxusIs, 



Graptolebris 



Chydorus 



"* Morwspilus 



fig. 1. — table illustrating the relations of the 

 Cladocera Calyptomera. 



*NOTE.— To adapt the diagram to the theory that the Lynceidse are the progenitors 

 of Cladocera, it is only necessary to revolve the imaginary lino to the right, till It 

 coincides with the axis of that family. The question mark may be understood to 

 indicate that the source of the pivotal group, Moina, is uncertain. The author must 

 confess that his inclination is toward a belief that the line culmin^vting in the Daph- 

 nidae diverged from a group of organisms resembling Phyllopoda, more definitely, 

 resembling Limnetes. There is a very remarkable resemblance between the larva 

 of Limnetes and Bosmina. The lateral spines of the former are, as will be shown 

 true homologues of the antennules of Bosmina. The later origin of the Phyllopoda 

 iu their present form may be well admitted 



1 Entomostraca, sen Tnsecta testacea, quae in aquis Danise et Norwegise reperit 

 dcscripsit, etc. Otho Friedric Mueller, 1785. 



2 Mouoc. qui se trouvent aux Envir. de Geneve. 



